I am contemplating putting a 1967 posi into a 1972. It seems crazy but is it possible or are the headaches not worth it?

not worth the effort. Just find one made for your car. You should have no problem getting rid of the rear end you have now.

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67 Convertible
97 Vette
Chevrolet powered boat 28ft Profile cat 502EFI Procharged with 13lbs boost radar 112 MPH

If you decide to do this you will need to relocate the spring perches and maybe modify the length of the driveshaft. I would at least attempt to find a rear end out of a second generation F-body, they are not that hard to find, plus they are much cheaper than a 1st gen rear end. I say get the right one and sell the rear end from your 67, I bet you will make a profit.

Steve R.