blkhrn - Don't know if this helps, but you can get a kit for $400 to convert the front axle to disc brakes and 5 lug from the six. I am doing that on my truck, the rear was replaced with a modern rear from hell knows what. So it rounds off the truck with good brakes and modern parts.
Seems like that is easier than drilling axles and better than adapters. I tried making adapters on my 62 Rolls, and it was lots of work and they suck. But that is my fault.
Here are some pics of what I did for adapters. I know its not for a truck, but still the same idea.
Wheel Adaptors, what not to do Seems like every time I try to do something profesionally, it reverts back to my bad habits and shortcuts. If you are the same way, just buy the wheel adapters already done.