The Corvette app is a rear trans type, I would suggest any of the others would be a better choice.
As for axles I'll tell you what I'm using in my 1-ton. Up front I'm using the IFS from. Chevy C20. I used a '72, but '71 to '87 are the same. This is the right choice for me but will result in a wide tall truck.
In the rear I'm using a GM 14-bolt on the stock springs.
I'm building a big motor trailer pulled and feel good about my choices. Something else may make sense for you, be sure to look at what Grigg has done. He and I usually end up in different places, but we usually know exactly why.
