You did say its a HO72, I must have missed that.
But I'm still skeptical that its a HO72 with 6.17 gears. I've never heard of a 6.17 available for the HO72 though it is a ratio offered in the Dana 60 which was offered in '70. Can you post a picture of your axle?
I don't have a copy of the options book you refer to is that book available online somewhere? If so can you post a link to it?
But we're getting away from my purpose in identifying the rear. If it is a Dana there may be a 10-lug hub available that can be adapted to it. That would make running the wheels you want a simple operation.
If it is an HO72 it probably has 1/2-inch lugs that are a little small to start with. Adding an adapter is going to put more stress on them and make breakage more likely. I know you are very committed to your existing axle, but if its an HO72 the smart move may be an axle swap.
Although having said that, I do know that there is some interchangeability between the HO72 and its successor, the GM 14-bolt. I don't know if that includes hubs, but since 10-lug hubs are available for the 14-bolt it might be worth investigating.
