Appropriate Wheel Offset for 18" Wheels?

Still running 10.75 stock 73+ rotors! Need to upgrade those ASAP. Keep hoping someone will make a 13" 6-piston kit for my 73+ spindles. I do run 1/2 - 3/4 inch of spacer, no problems with frame rail clearance, doesn't rub, but haven't measured it either. My rears are 19x10.5 with a +25 offset....

When I get my Dart done and autocross prepped, I'll let you drive it to see if Dr Diff's kit is enough braking for you.