The throttle bracket and rod that goes from that to the carb on the piece 318/904 setup is different between 4bbl and 2bbl and the rod is also different between type of 4bbl. The rest of it is the same between 904/727 except for the bracket that bolts to the transmission. I forget what its called (torque shaft throttle shaft or something?) but I always call it the pivot bracket.
I don't know what changes between big block and small block parts.