Appropriate Wheel Offset for 18" Wheels?

Digging up this old thread. Really appreciate the guys stepping outside the norm and fitting up bigger wheels for grip performance.
I just picked up a set of aftermarket wheels front 18x10, +40 offset, and rear 18x11 +52 offset. Came off a newer Boss 302 mustang. I'll be tossing these on my resto mod 69 GTS 383 car.