I am totally against frame "swaps".
1. There is no such thing as a frame "swap", either it's the correct frame and it swaps in or it's the wrong frame and it requires a TON of work and money to make it work.
2. All it "swaps" is money or money or time for time, the same money and time spent on the stock frame will produce a nice driving truck.
Even a dropped axle set up properly provides a pretty nice driving truck, how much better does it need to be?
That is your decision, what are your expectations? Do you want a new truck that looks like an old truck or do you want an old truck?
I personally love driving the old cars, they have character. I have my wife's mini van when I want late model transportation. But driving a vintage car is a blast to me, what is it you are after?