I'm not a fan of these big rims but for each his own. I also have no idea what 1 mm offset means.

What I can tell you is that I had 15 x 8 rims with 4.5" backspace with M/T ET Sreet Radials P255/60/R15 on my 67 Coronet 500. Around turns it would rub the quarter panel lip. Probably a 7" rim with 4 inch backspace would of worked as the section width decreases with the smaller rim, but I went with a 7 inch rim with 4 1/4 inch offset. No problems with that.

Not sure how this helps you with your selection.............