Just food for thought for You, when Mopar was testing it's B/RB Purple Shaft cams, they used a Dart Sport IIRC w/a 400 B engine auto & an 8.25" SG rear.....launch after launch after launch.
As I've posted before elsewhere, when I decided to put a '68 B-body 8.75" in My ex-Popo Diplomat, I went out on the ridge the night before pulling the SG 8.25" & tried to break it, 383 4-speed tach it up dump the clutch power shift into 2nd stop as soon as it quit spinning & do it again.....over & over & over..... so many times We finally left before one of the farmers called the real Popo!!!! My buddy was there with His truck to pull Me back home....never happened. Granted, this wasn't on a prepped track w/slicks, but I beat the bageezus out of that rear including bottles of N2O. Best value for You is 8.25" Mopar or 8.8" Ford.....Folks want a lot for A-body 8.75" these days. Best of luck whatever You decide, peace!!!