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.
That's exactly what I was told about my A body 8 3/4. If I was gonna pay to cut it up and rebuild everything, I could spend about $500 more and have a Dana built, so I sold the stock A body rear end and built a Strange 60.
I may be wrong, but I wouldn't stick a bunch of money into a 8 1/4 rear end that you're gonna run big tires on?!?
