55.2-59 What’s the most practical way to swap engines?

[Phungki]

Ok so I finally found a project truck. 56 GMC stepside. Body is really good considering the age. Floors are unbelievably solid. Cab corners are shot but fixable. Front fenders need some love or just replaced. Interior is wasted but that’s just cosmetic stuff that can wait. For me the first order of business would be a drivetrain and brakes.
I was thinking about a 350 w/700r4 trans. What’s the most practical way to go about it? Is there a certain year of engine/trans I should be looking for? Best mounts and/or crossmember to use? I do not want to change the front suspension. I will eventually put disk brakes on the front. Was thinking PS/PB as well eventually. Other than that i don’t plan on veering too far from stock.
Thanks in advance