Rear end swap questions...WWYD?

[budman k20]

I'm building a 67 c10 (with 49K miles) that has a 6 lug posi rear. I also have a complete 72 chassis to swap out mileage unknown. I have read up and searched converting 6 to 5 lug rear ends. Both rears have 3:73 gears, and I want the posi either way. So I have to either put the posi unit into the wider 72 rear or put aftermarket 5 hole axles in the shorter 67 rear. I think it would be less work to put axles in the 67 rear.
So my questions are:
Would you use the 67 rear and why?
Would you use the 72 rear and why?
Are there fewer wheel backspacing options for the 67 over the 72?
Can I just bolt in the posi carrier in the non posi rear and not have to reset the ring and pinion gears? I'm guessing I would have to re-shim for backlash but not have to change pinion depth...

I plan on using the complete 72 disk 5 bolt front end.

Thanks in advance for helping me decide what to do!