The most important aspect of this type of modification is doing your homework. You should have everything planned out before any work begins. Hours of planning will save days of work. Getting the right donor is super important. I did a '47 Ford truck for a friend who found a donor '72 Nova with a fresh engine and trans. I put all of the Nova stuff in and under his truck while he was in the Bahamas for two weeks. I used the entire Nova frame clip, electrical system, tilt column from an auto recycler, rear suspension, power brake system, and all. The only thing I had to farm out was having the drive shaft made the proper length and balanced. When my friend got home from vacation his truck was in his garage ready to go.
Mind you, I spent all of my waking hours for two full weeks, and this was not my first rodeo.
Again, homework and planning are the key. Surprises are most always bad.
No, since both of us retired, I don't work on other folk's cars any more.