Do it and don't think twice.
I would prefer to find a swb frame if I did it myself, but they're not always easy to find, but you could save yourself some money in the long run:
Consider this:
Most people want power disc brakes. 68's don't have that, at least not disc.
Most people want 5 lugs. 68's have 6. Even if you bought a 5 lug disc brake kit, you'll still have to address the 6 lug rear end.
Most 68's didn't come with power steering, most 71/72's did.
Factor in all that stuff, and the FACT that a shortened lwb or a factory swb truck in the same condition/options as a lwb truck will ALWAYS bring more money on a sale, if you want to do it, do it.
My point? It may cost $3-500+ for a good swb frame, but factor in everything above, I think you'll be ahead of the game if you find a good
71/72 swb frame with disc brakes and 5 lugs. Make sure you take measurements to check for square, always question why a good frame is for sale
