Thank you all for your advice. The Eldorado tranny/axle would probably hold up if I didn't load down the truck or abuse the gas pedal. The better choice would be to install newer truck axles with appropriate brakes.

Since this is my first go, the semi-stock running gear is my choice, but...

The 20" split rim/tire combo is a concern.
My spare tire weighs 130 lbs! (I weigh 120)


When I find out what I'm doing, I'll let you know if I'm in too deep.