Decent handling susp setup?

The 68-70 B-body 8 3/4 I run is 60 1/8" drum to drum. The rear wheels I run are 18x10's with +38mm of offset, so, the actual track width measured to the middle of the tire should be around 57 1/8", but that measurement doesn't help much with buying wheels. And to fit 18x10's and 295's I did a 1/2" spring offset and cut a bit more than a 1/2" off of the quarter lips.
nice, one of the things I've been considering is switching out my 8.75 for a b body in my dart. Im running a GTS front kit as im sure you recall in our numerous discussions but I've been wanting to figure out a better way to widen the rear track some before I fully weld in the rear 4 link setup. I'll be running 285s up front and will most likely be flaring the rear quarters about an inch to two inches.