HI EVERY ONE, OK so the question is: What is the origonal tire size for a 1978 Mustang II. The tire sizes on the car now are (P185/70 R13)&(P185/80 R13). I supect thes are pretty close. What is intended is to use the 10 spoke alimnium 4 lug from a 1985 Mustang GT. For the newer 10 spoke I plan to use eather (P205/60 R15) or (P195/60 R15). I know some has tryed this because I have seen photos of a MII with those mags on it. I need the information for tire size calculation. I hope this stuf makes sence ? Thanks.