Disc brake upgrade
Maybe look in to some wheel adapters?
The problem is that wheel adaptors that are worth a crap are at least 20mm thick. Most are actually 1”. Which then makes the backspace an issue, it basically means buying new wheels anyway. Because what you’ve got won’t have enough backspace to handle that kind of adapter.
Assuming you could find a BBP to SBP adaptor.
I actually think your better option would be to convert to the 73+ spindles and 11.75” BBP disks, but have the rotors drilled for the 5x4” pattern. That’s what that MBM or PirateJack kit is doing. They use a 73+ disk conversion but have the rotors drilled for the 5x4” pattern and turn the hub register on the rotor down to fit earlier wheels (some of them anyway). Your aftermarket wheels might not even need the hub register turned down. I mean they do it from rotor blanks so the other pattern isn’t there, but that doesn’t matter. Just press the studs out and have the new pattern drilled.
Sure, every time you replaced the rotors you’d have to do it again. But I don’t think the re-drill would set you back that much. Heck the 13” DoctorDiff cobra style kit I have runs corvette rotors re-drilled for 5x4.5”.
