8 1/4 suregrip and gears

Darc;
Not sure how much you are into wrecking yards, but the 8.25 from a pre '91 Dakota will fit your rear end.
Did it myself for my '75 Dart.
Donor was '87 Dakota 2 wheel drive with 8.25, SG, 3.55's.
Direct bolt in. $100 plus bearings.
If you go this route, some notes for you.
Use the differential bearings from your carrier. Same with the Slack Adjusters. The ones from the Dakota do not fit. Be careful, they look close enough to fit but the don't.
Pinion bearings are the same.
Don't forget the new crush sleeve.
I was in it under $190 for the whole mess including the new gear oil, bearings, donor parts, seals, and gasket!
You can check with 69MOPE, I think there are some others that interchange, but this is the one he pointed out for me.
Cheapest Gear swap I have ever done.