46gmcpu & Coffeeman - thanks for both your replys.
And i've already been thinking about finding a fairly complete donor vehicle and doing a LS swap. Only thing i fear is the troubleshooting aspect. But, i's sure there are some relatively inexpensive diag tools on the market. Lot's of food for thought here.

Here's one route i've been considering; go ahead with the 350/350 swap for the time being and try and find a rear axle assembly with a ratio that would work well with the 350/350 and a future LS/4l60 and save money and study everything i can find about an LS swap.

This way, i should have a better understanding of what will be involved with the LS swap and can keep my eyes open for the right doner vehicle, and i can 'enjoy' my panel and can be working on the interior and be repairing/replacing any of the body parts that need updating.

And while we are here, what rear axles will fit inside the rear fenders of a 1950 3100 Chevy panel truck? And what rear axle ratio would be a good compromise for towing and normal highway driving?

Thanks,
Mike