71 dart 17 inch wheels 5x4 bolt pattern

Allright I found pics on here of a 71 dart with the wheels I want. He said there 17x7with a 4.25 backspace with 225/45/17
He didnt list the offset but according to the catalog its +6mm. But they also offer a 17x8 with a 4.5 backspace with a 0mm offset. I am I better off with the 17x7s or do I need the 17x8 for the o offset