My only thought would be screw in studs for the 1/2-20. Easy to find in different lengths.Depends on if the shop would want to instead of knurls.
I have a 72 Dart base Slant that is in the body shop for at least a year. Plan to do the disc swap up front.
Was going to start to look for the big bolt 7 1/4 or 8 1/4. But for $100 I'd run adapters on rear as the car will stay stock.
Plus it would help with the wider stance from the front disc swap. Even things out . My 2 cents.