In the tech for a 73 blazer it list several 3 speed trannies. Which i have figured not many people have in 4x4s but how do you know what kind you have and to swap to a 4 speed what the adapter will bolt up to? It came from the factory 350 3 on the tree 205 44 front 12 rear with open 3.08 diffs. /forums/images/graemlins/dunno.gif