Thanks HP2, you are quite the man at tech.
I maybe looking at a 16" rim. Stockton have cop rims in sizes up to 17.5". The reason I want to upgrade to 16" is because I wouldn't mind running 295/50s and it will allow a bigger disc. I would get 295's on my 15x10 but I am not a fan of that low squashed "fat" look. The OD of a 295/50/15 is 26.7" where as my Challenger's 275/60's are 28" which is 1.3" higher there fore giving the car a leaner look, stock but more lift out back and a slight rake. These cars (IMO) look shocking when the rear ends are sagging low, looks fat & heavy, not my scene. Another draw back is you can't raise it then you get a wheel lip to tire gap & that doesn't look too nice IMO, OK in the 80's not now.
Anyhow, BFGoodrich make a 295/50/
16 with a 27.6" OD which is 0.4" lower than my current 28" OD tires, still
very close to how my Challenger/Cuda sit. So I will get Stockton to make the rear 16x10" cop rim wheels, order the 295/50/16 BFGs. Before I do I'm going to call Dr-Diff (soon) and ask what backspace I will need to get it about 1" from the springs and lip using his Dana-60 from a B-Body, he'll know which year to get a perfect fit.