Help With wheel tire combo fitment!

so wanna go 18 inch wheel on a 70 plymouth duster but wondering will a 18x8.5 with 6.25 inch backspace 1.3 inch offset running a 255/35 or a 255/40 on all 4 even fit?

stock suspension 8 3/4 rear..discs up front drums in the rear..stock spring location!