8 1/4 Rear end Narrowed locally?

I have a 1970 duster, with a 8 1/4. I upgraded to Weld Draglites 15x14 with 7.5bs on 31x18.5 MT Sportsmans.

Why not just get the rear wheels with the right backspace/offset.?

Does your 8 1/4 rear have a sure grip and the gears you eventually want?

If you are going to put a bunch of money into narrowing, gears, limited slip...It better spent money into a stronger 8 3/4 rear with the grip of those tires.