Putting on either of those mufflers will make a HUGE difference in the bikes performance...when done in conjunction with the carb jetting.  You will need to go back and tune/rejet the carb again, but it is well worth it.
I would also suggest going one size larger on the pilot jet.  I consider that to be the #1 jetting priority, 2nd is removing the white spacer, and then making sure the main jet is the proper size...just my opinion of course.  
Your main jet, at 152.5, may be fine as is but you need to check to be sure.

A sportster muffler gives a little less performance to a Savage when compaired to a MAC or other higher end exhaust system. One other factor you need to consiter is the noise level, a very loud exhaust can sound cool riding around town but on longer trips it can be a real pain for the rider. I've lost a good bit of my hearing to loud motors over the years and am trying to protect what is left. I've been using a sporty muffler for over a year and am happy with it but there are others who don't like them. Lancer is correct in saying that the rejet should be done in conjunction with the exhaust change, one without the other can cause problems. Luck with your bike

The MAC site lists their muffler for 86-87 Savage only but I assume it fits all years.  http://www.macperformance.com/store/product1.cfm?SID=3&Product_ID=669
Is this a straight bolt on using the existing bracket?  And how much louder than a stock Sportster muff is it?

rokrover wrote on 12/31/69 at 16:00:01:

It fits my 98 just fine.  It bolts right on (though you should loosen the header while you're getting it into place) and is pretty loud.  I have no idea how it compares to the sportster for volume.  Check out the tech forum to listen to a sound clip.  It's not the best clip but I made it using a long cord on a cheap mic running from my PC through the hall and out into the garage.  At least it gives you an idea.  I also hadn't fully tuned the carb at that point but it was decent.  I recommend replacing all exhaust gaskets when you do this.  You'll be much happier with really good seals.  If you have leaks, you'll get backfiring.

I got one and took out the baffle.  Its loud as heck but its faster.  I kinda wished I left the baffle in.  Too late now haha.

Wow I like it.  I like it alot hahaha.  Too bad its 450. OUCH!  It looks kinda big to mount too haha

That is an interesting twist on the theatrics of motorcycle parts sales.  

It will be interesting to see what the actual performance numbers are.  I also wonder about how long the barrels will continue to spin as the miles add up and the exhaust soot clogs up the bearing surface.

When looking at the specs of the muffler, it gave the length of it but I did not see what the diameter of the "GUN" is.  Did anyone else see what it was?

I do like the sound of it, which is very similar to the "Performance Design" muffler I have, which also uses a spiral design (first on the market several years ago) to create back pressure at low rpm and a vacuum effect at high rpm for max power.