I've got a 66 289 and am not sure whether the engine is an A code or a C code because the tag is gone and key parts (like the intake manifold) are not original to the car (its part no. is C8AE-9425-B). I want a good stock carburetor for it (it's current 2v one is a mess) and am torn between the ponycarb. autolite 2100 and the autolite 4100. In terms of performance and reliability, is the 4100 worth the added expense of replacing the intake manifold?