8.75 durability for big block street/ Strip

Imho, a dana swap increases the value of any mopar. Not so sure if that is true for a nine inch. (And I have two nines in my cars, neither a mopar tho.)
Edit: If you can do your own narrowing, I would narrow the c body to a body specs, put some Dr Diff big pattern axles in it and sell it . If you can narrow your own dana, there is no reason not to go that way, and a do-it-yourself truck dana can be a lot cheaper than a strange, just a little harder to set up.
2nd edit: there is no way in @#$% a nine with decent parts in it (meaning as strong as a dana) is gonna be anywhere near as cheap as a do-it-yourself dana.!