I'm running American racing 14*7 with 225 width tires all around . Unfortunate rear tries touch the body with heavy weights ppl in the car 😅.
A wider/bigger wheels requires diff modifications!.
Check this guy ING simon_883110 he has same as ours and running 17*8 wheels with slightly modified foxbody 8.8 diff and mustang ll front end
FYI, the width of diffs:
8.8 OEM : 153cm
63' skylark : 147cm
His custom : 143cm
I would suggest first you determine which direction you want to go with your car as no plug and play kits nor spare parts are available for 61-63 skylark/olds F85 available in the market. All requires fabrication and a heavy budget to make it work!.