I have not tried but have been considering if I choose to save the 1951 rust bucket parts truck. I have access to several 265s and 235s laying around. This is a project several years off...
SM420 (and I think the other 3 sp tranies ) will bolt into the back of 265 v8 manual transmission bell housing (so I am told)-- Then the question becomes the firewall and being able to actually bolt it up to the torque tube transmission/drive train (if you wanted to keep the same drive line).
--- cross member at bell housing will need to be manufactured as pointed out by Hot Rod Lincoln -- and if you move engine back, then the same for front cross member for 265-v8 front motor mounts
the starter/ignition switch. If I do this, I will probably use a push button starter switch with same ignition switch. So you will need to do some more research on this.
Steering box: the steering box will not need to be relocated as I have seen advice given stating for people swapping in a 283 to use a 265 exhaust header on the left side. It may just be the 1955 left side header, .. could not nail that down.
then the rest of the things people do for switching to a V8 and addressing some of the weaknesses of the 265.
and the advice above about the value of a 1955 - 265 block
Last edited by Kilted54; 05/15/2017 8:51 PM.