You have dug deep into this stuff so you get it and posted the differences on blocks shafts and other cool stuff in addition to the basis color offerings........... In a lot of cases, a good quality billet/cast modern day carb will serve most very well when calibrated and tuned in on your car/truck.........And then there is the high end billet main bodies and the best components available but most don't really need em but they sure are sweet..........