[steverino66]

I put a big block in my 66 truck, had to re-drill frame holes for perches moving the engine forward a bit (used the taller perches from a 71 truck for left side header clearance).
On the 700r4, the 350 yoke will work; depending on 350 tail section length, driveshaft will probably need to shorten 3" and the crossmember for rear mount goes back same amount on the frame.
You can get a converter lockup switch kit from several sources, Jegs, Summit, etc. The trickiest part of that trans install is getting the correct TV cable geometry between the trans and carb - if you have carb, manifold/bracket from a factory orig. setup, great, but if you use an aftermarket carb you may have to get a kit from bowtieoverdrives.com. Fluid pressure controls your shifts and TV setup has to be precise. I put one in my El Camino, but I've read you won't get huge mileage increase in the full size truck.