Wire up a 5.9 FI Magnum to 60's A body.

The first issue if you intend to use that transmission, is chopping up the floor/ crossmember. It ain't a bolt in. Guys have done this but unfortunately documentation is flighty. First thing I'd do is get a service manual for whatever the engine came out of. Second issue seems to be "if" the original vehicle had "security" and I think that boils down to a key fob.