AFAIK the answer is no. You could re-drill the hub for 4.5" LBP, but it may not be the best solution. If your car is equipped with factory 4" disc bakes, you have the Kelsey - Hayes 4 piston - fixed place calipers with the 2 piece rotors (detachable rotor hat). Most of the conversions i"ve seen appear to deal with SBP drum brake cars by allowing you to keep the 4" SBP (Scarebird conversion comes to mind) spindle, while substituting GM pieces for caliper and rotor with a caliper adapter bracket.
Hopefully someone else will chime in with good info!
