1966 valiant v8 swap?

Welcome, Depending on HP you most likely get by with a 904 trans. If I remember right there is some mods that need to be done to fit in a 727 sb trans. You will need a V8 center link and motor mounts to drop a 318 in. A 8 1/4 A body rear or better yet a 8 3/4 rear is work ok. Check out the Early A Forums for more there is a lot of info there on V8 swaps.