Those short 4500-4150 adapters look like they'd be so restrictive that you wouldn't see any performance increase from the bigger 4500 carburetor.

Looks to me that if you can't use the taller adapter with a smoother transition, then you'd be better off staying with a 4150 carb or getting the a 4500 flange manifold. CHIP

Holy crap that seems like a lot of money for that spacer. I wonder if they priced out the same one as mine- if so that's a hell of a price increase. Personally I don't think it's with it for that price(allthough I'm not sure what else a guy can buy that is that short and still decent)