71 Demon 15 x 10 Backspace Question
the measurement to the spring is ~ 6 13/16.
You need minimum 3/8 for clearance from the bulge
to the body to allow for sway in the corners.
my 295Coopers on 15x10 are a lil over 12.6 across the bulges; so 6.3 from the centerline adding the 3/8 = 6.68 So you are cutting it pretty fine with a Zero offset wheel, which is 5.5 backspace
So all in all I think 33IMP is right on target
Yes I run 24psi for long tread life, cuz honestly 10s are almost too narrow for 295s. At 24psi, the car will roll over the sidewalls during modest cornering, making the back steer the car further into the turn than you expect. Watch for it cuz it is a lil unsettling till you get used to it.
FYI
For straightline action 275s are adequate up to say 350 hp. I only run the 295s to get sideways rubber, so that if I get into trouble in a corner, I just lift off the gas and let the tires couple,and then I'm not in the weeds again. I hated that,lol.