As Fibonachu said a frame swap is a much bigger deal than a driveline swap. I am doing a '50 3600 that will be a SBC (Gen 1 not LS) with an NV3500 5 speed manual and a 4.10 Chevy 14 bolt rear axle. My goal is to basically have a 1950 looking truck with a more modern (but not current computerized technology) drivetrain. I changed to disk brakes up front but retaining the drum brakes on the rear. I am keeping the original leaf spring suspension.
There are some other projects you will find here that have done frame swaps, the most common being from an S10. Most current frames are too wide unless you want to stretch things side to side (a bigger challenge).
There are a fair number of LS swaps that you should be able to find information on here with the balance of the drivetrain a mix depending on what was desired.
The rear of the 3600 frame is narrow compared to the 3100 frame so that impacts what works for under bed fuel tanks, rear axles conversions, etc.
