Upgrade for '70 Swinger 340 rear

Many thanks to all over the years(!) for the help on my '70 Swinger 340. My 408 is in the end stages of construction, I have a Pat Blais built 727 with a freshly built FTI 3600 stall speed hard hit converter. Time now for the rear end. The stock open 3.23 8 3/4 will ned help for the mostly street driven 500+HP small block. I also have a complete 8 3/4 with a 3.23 SG I picked up years ago. I'm thinking of rebuilding the spare rear with a 3.55 SG and new SS springs. Maybe Caltracs? Looking for advice from my FABO family for the most important part of the traction puzzle. My hide is as thick as an old Santa Gertruda, so let your opinions fly! It's been quiet around here lately, so I thought I'd kick that hornets' nest! Ford 8.8? Dr. Diff? I'd like to utilize what I've collected over the years, but I want a badass, stock looking 1970 Swinger 340. Thanks to all in advance.