Hah! Yeah, I've got my rebuilt 904 sitting on a dolly in the garage (the non-inflatable type :lol:) and I'll have the old one out of the car here shortly. Of course I have two rear axles sitting here as well...
If you swap a 318 in there, you should upgrade the axle as well... I blew up three 7 1/4" axles with a mild 318 with a 4 bbl and dual exhaust... I then went to an 8 3/4" axle and never blew one of those on the same 318 for over 200 k miles...