there was a (related) thread on this yesterday & iirc the SBP discs have the same track as the SBP drums so this is what I was thinking, if you had SBP discs (I'm sure it'd be cheaper than the other (SBP) disc options, you could look at the SBP rotors (front & back sides) & see if there is room to redrill em to 4.5" which is only 1/4" outward at any point on the circle perimeter from the center and you'd be going to 1/2" wheel studs. if all good on that potential you could drill the 5 new holes on your drill press & a tap is cheap as is thread in 1/2" wheel studs. If that becomes a go holler & I will give you the simple math to locate 5 pinpoint marks to do your drilling. LBP wheel registers (center hole) are larger so you'd just need lug centric lug nuts