OK- Although I got the carb as I was mounting the billet intake- I first tested just the billet with the old carb to be sure of what is doing what- Remarkable improvement in carburetion!
I would say, for the money, (I paid $10 plus shipping, I think they've gone up to $11)
the short alloy billet carb intake is the single best improvement, at least on engine performance. (I still swear by $10, 1.75 wide tires for the roll). The billet gets the carb much closer to the engine. I reamed mine out further until the smaller carb side at least felt as wide or wider than the stock intake opening. The motor side is much wider and more matches the motor ports- if you cut a new gasket to match as well at least.
I'm two stroking now at will consistently and still have yet to try the new NTS carb with the larger ports and jet.
The drawbacks- you have to cut the clutch cable bolt under the carb for clearance, and lowering the carb cuts down the frame clearnce slightly- the NTS will barely clear my frame even though the billet itself is shorter.
As far as motor mounts- I've used that flexible pipe insulation styrene-type material with excellent results- I think it is more absorbing than rubber, if the right thickness- about 1/8". And it cuts real easy.
You can see the billet a little bit here: