Wouldn't go bigger than 2x28 possibly better is a 2x26.
From a money point of view a Mikuni VM38 with a UFO and dial-a-jet from Lancer would give good performance.

Clive W  

You will buy Yourself a lot of trouble for nothing.
All of us are fans of the simplicity- why mess up with it ?
There are many things against the idea, but I'll mention only couple:
These bikes don't use 2 real carbs, but one real and one secondary- it is more like running one 2-barel carburetor. This set-up is actually supposed to give You better respone at low-mid range and better fuel economy at lower loads.
Have You ever checked what is the compression ratio of these bikes
How many bikes with this set-up are still in production
How many horse powers make similar bikes with 1 carb versus with 2 carbs
2 carbs mean 2 intake manufolds- totally different head.
why do You need 2 carbs on a bike with compression ratio 8:1
have You ever talked to a mechanic that has worked on one of these bikes and asked for his oppinion
Even if You make it Your carrier oportunity and your  life project and You do it - what will be the   "HP increase/ $ ratio" ? I bet that going to 0W-40 full synthetic oil will give You better result.

Lot's of work & $$ and unknown return on the investment.  I would agree that a totally new head would be required in order to even consider doing something like this.  If you are a machinest and are in need of a project..........otherwise, the current head design does limit us greatly.  I am hoping the porting and compression bump I did on this current head will perk it some more, but only time will tell.  
Anyway, it is just my opinion, but I think that doing things like the porting, mod perf cam, exhaust, intake/carb, and such will pretty much maximize the potential of the Savage...short of something like a supercharger but then you have to be concerned about the high pressures applied to the parts.

Thanks to all who have replied so far... Though most response hasn't been too positive.  As I stated, I'd thought about this far more than I had revealed, and so far the discussion has only touched a couple of points beyond my previous considerations.

The loss of simplicity in doubling parts and having to sync carbs was a given which I'd really hate to give in to, but is not beyond the realm of possibility. I've been up for the "complexity" of twin cylinder, and even multi bikes in the past, but I agree that the simplicity of the Savage is possibly it's most appealing attribute; so I can certainly understand a "why mess with it?" attitude.

I agree that 2 x 28mm would be pushing the concept to the max. And even at that, there would need to be improved flow through the head, and optimized valve timing (better cam) to realize much of any possible potential. As for having to change the head entirely: I don't think that would be an absolute necessity. I think manifolding them together pre-head would work, but the result might be less efficient than a well tuned single carb. Hard to say without a flow bench, or going there.

Greg's semi-serious(?) comment of following up with dual exhaust ports, and pipes, had already crossed my mind. But then you really do get into "a whole new head" territory.

As Slavy mentioned, not all "dual carb" systems are created equal, and I believe he is correct in that some work on a two-stage principal like a four barrel automotive carb with vacuum operated secondaries, or an old "tri-power" 3-2 barrel setup with mechanical linkage which only kicks in the front and rear carbs when the throttle linkage passes the 2/3 to 3/4 mark. And I could see how trying to set up such a "staged" system, using two individual carbs would be an extremely difficult to impossible task. I must say however, that such staged systems do have benefits. But I would dismiss any such staged system as impractical for a DIY shade-tree project, because it multiplies the complexity. So... that relegates any dual carb attempt into an "equal halves" arrangement which may be of completely questionable value; at any price point.

I also agree, that porting/polishing and raising compression are no doubt much more cost effective and direct paths to HP gains, and perhaps with little or nor loss to low end torque. In fact, if done correctly it might be win-win all across the board. The best of all worlds!

Even the possible cost of $400-$600 is not a complete killer to the daydream of having one of a pair of twin carbs angled out of the frame on each side. How cool would that look?

The real dream killer, may be in what Dr. Jim mentions in comparison with the BMW... Yes, who wouldn't love to have more HP, but how much lovely low end torque is to be sacrificed to possibly make an engine that is RPM hungry and "peaky?" Since grunt is much of the attraction of the Savage: I'd say that very little if any loss of that steady low to mid RPM tractor power would be acceptable unless it was in trade for huge leaps in HP. And even if it was wished; due to basic design limits, making the Suzuki motor into a 7000rpm cruising rocket just isn't in the cards.

But if not for purely performance reasons, but aesthetic considerations... dual carbs might be interesting. Providing that they didn't cost too much in way of performance; increased maintenance, and yet unmentioned fuel economy. I know that I'm getting little enough distance out of the small tank now, without reducing mileage by some  percentage.

And still, with all these things said, I can't help but wonder...  

If you really want to find out how bad balancing carbs can be get yourself pre 1980 british sport car. If you drive it everyday, you'll be balancing carbs on the weekend and running terrible by Friday. Good news is after a while you'll get to the point where you balance them "by ear."

I really don't think the appearance of two carbs would be worth the additional grief. Also who knows how long a Savage engine would hold up under the additional requirements. It wasn't made for that.

velocity reaps gains where volume cant

The Honda X/L 500-650 thumpers with RFVC 5 valve?  heads had the progressive carb set up. Essentially it ran on 1 small carb for good throttle response and idle quality. About 1/2 throttle opening the 2nd carb was opened and they both reached WFO together. WFO would really hustle those heavy dirt bikes. But in my experience was they were miserable to start. No electric leg, just hold the monster upright, on your left tiptoe, kick fully with your right leg maybe once, or maybe until you could care less about a ride. If you fell over in process, may want to wait a day until the fuel had a chance to evaporate and try again. I'll take the one carb Savage any day. I've been riding B-i-L's 88 with what we think is one of Lancer's carb kits on it. It sure idles nice and is smooth spinning up with no hesitation or bogging, but the air intake roar almost makes it sound like the clutch is slipping to me. It has a cone filter on it.