I am building a 54 with a 2003 5.3, drive by wire, 4l60e and 75 camaro rear end with 3.08 gears. donor truck had 65K miles. engine, trans, pcm, tac module, throttle pedal, compete wiring harness, fuel injectors and lines set me back 1600. I think the ls based engines are the way to go.
I just noticed your setup. An overdrive with 3.08 gears will probably have your RPM's much too low and your engine will be lugging, unless you're running 38 inch tires, or at 90 MPH. You may want to consider 3.42 or 3.73 gears with that setup.
you miss the fun of driving if you use all that modern stuff
try following Cletis around with the modern stuff and
see how hard it is to keep up with him.......................I know.
In my family we have several collector vehicles, some from the 60's that are more original, and some from the 30's, 40's, and 50's that are rodded. In no way is it any less fun to drive when the car is rodded. To each their own, and I can appreciate it either way, but if I can't go at least 100 Miles at 65-70 MPH (sometimes 80-85) reliably every time I start my truck, I might as well not have it.