Shawn, seems like a lot of pain and not much gain . You have a motor that as stock puts out nearly as much hp as a 650(stock) ,and it's water cooled,why would you swap? The height of the 650 is20" front to rear15 5/8" don't no the width,but it would be close to your twin I would think.I would think it would be much cheaper in the long run to buy a used 650, which would come the all the engine mounts, cables ,handle bar controls ,shift and break linkages ,ign. and charging electrics in place,and then retro fit parts from the Barhog as you see fit .Parts are out there to convert the S40 to a "barhog"
but the other way is all custom fabrication .

An engine transplant can be done - but it is a complicated job, often requires fabrication and welding....and you end up with an engine we can help you with, and a chassis that still has a problem with obtaining product support.  And.....the charging and electrical system will most likely have to be a combination of the 2 bikes.

You could end up with a good motorcycle if you sold your PAG and bought a used Savage.  Really nice used ones are $ 3,000, good running motorcycles are available for $ 1,500 in most areas, fixer uppers can be had for $ 500.  If you are new to motorcycles and wrenching....it will be better to save up for a newer/nicer model that is roadworthy and doesn't need repairs (just routine maintenance).  It is not uncommon for the engines on older bikes to have worn cams and rockers, oil leaks, and potentially stripped head cover screws and/or exhaust header bolts that are difficult to repair.  The engines can last a long time if cared for - they are fairly expensive to repair if they are broken. 

I will have to do just that it seems. I do like that bolt on hard tail kit from the company that was posted here. So I may finish servicing up the Pag and sell it while the gettin is good and hunt down an S40. I gotta keep reading in here and do my homework so I'll know what to look for. I've brought alot of Vintage Japanese bikes back from the dead. Like triple two stroke Suzuki's, Triple and 4 cyl Yamaha's and a few CB's.  Love doing the work. So this Thumper Hardtail should be a fun project. Thank you for all the replies.

Shawn,

Blue Collar Bobbers has a really nice Bobber kit too. Lance and his wife are a real pleasure to deal with.

http://bluecollarbobbers.com/catalog/savage-s40

Kenny G

Awesome options, thanks guys!  Now, I gotta find thumper!!  That big ole single jug, just screams bobber!