It looks like you are able to pull this frame modification off, but that doesn't mean that is a good idea. There are bound to be unseen unintended consequences. Something along the lines of "no free lunch".
What do you plan on doing with this truck?
A friend of mine had a '57 NAPCO which has the riveted on crossmember for the transfer case, indicating that it was set up by Chevrolet and not an add on kit. He drove it like he stole it. He went through several transfer cases and a transmission, but he did not have any issue with the front axle bottoming out. His truck came with extra leaves in the spring packs front and back.
