Engine swap

[66folks]

I am in the process of trying to find the cost to rebuild the 305E that is in my 66 right now. The couple of estimates that i have been able to get so far have been around 3k. That is a little more than i want to spend on a rebuild. I have a 74 Old's 455 at my parents house that I'm trying to get either shipped or driven down to me. My question is how much trouble will i have getting it to fit in the truck. The engine was in a 82 Cadillac that originally had a 350 turbo diesel in it. I know i will have to get different motor mounts but will the tubular ones that a lot of you guys use work the Old's motor? And depending on which transmission I have will determine if mine will work.

Ben