ET is offset from the center line of the wheel, are you really looking for 55mm and 60mm offsets? Do you still have the 5x101.6mm brakes or are they upgraded to 5x114.3mm? I assume 5x114.3mm, so if that is correct what was used to convert to that pattern? This info will determine if you track width has changed. What rear are you using and also how was it converted?
FYI I run a 17x7 from with a 19mm offset, that was for 73-newer 5x114.3mm brakes. Rear is 17x8 with a 35mm offset with a factory A-body 8-3/4 rear converted to 11x2.5" drums.
Your best bet is to measure your car.