Im going to put 18x8 wheels but I need the wheel offset. My car is in resto phase so I am unable to measure.

Thanks

You didn't state front or rear or both, although in my opiion in shouldn't matter. You also don't state what tires you will run and this is important to know.
I would center the wheels, ie, 4.5" offset.
I've got 17x10's and 17x8's on my 67' and nothing rubs anywhere. If your tires are no larger OD then mine, 275's and 245's, it shouldn't matter that your rim's are 18's.
Dennis

I agree with Dennis. An 18x8 wheel with zero offset/4.5" backspace should work fine.