Narrowing Rear end for a "Fat Lip"

[LUACE]

I am looking into narrowing my rear end for my 68 Camaro (Mini Tubs and BMR torque arm), hoping to get that “fat lip” look. I believe the standard length for a first gen is 60” and considering narrowing 2-4 inches on each side. Since many of you on the site have already gone through this I am hoping for some feedback to avoid irreversible mistakes. I’ve heard that narrowing can cause wheel flex and braking issues and other complications, so I want to make sure I don’t cut too much. In addition, I am looking for what size wheels and backspacing you guys are running. Thanks.