Magnum 500's ('70 mach I)

[johnanthony]

i just purchased a california manufactured 1-owner 1970 Mach I. i want to replace the stock steel rims with a Magnum 500 wheel kit. should i go with the 15x7 (i think 4 1/4 backspacing) or the 15x8 (with 4 1/2 backspacing). tx in advance for your help. -JA