Reply to "#9402 Master Brake Cylinder - GT5-S"

Lui, my GM/Byars power booster was happily rebuilt by Bob Byars in CA for the cost of the part when it cracked a plastic air valve on the pedal side after 2 yrs (which may have been my own fault). I'd call him first if your unit has problems. A stock 4-bolt GM will likely not bolt into a stock 3-bolt Pantera, and changing the booster bolt pattern requires the entire new assembly be torn down for stud welding. Byars also gold-alodines the finished assembly for a professional look.
FWIW, a Byars-modified booster fits Pantera Ls without dents but early cars did need some 'hammer-massage' to fit slightly larger diameter booster cans. I had trouble with a factory Gr-3 installation that also uses a bigger booster, in a pre-L. But since your Pantera is apparently a late wide-body with potentially everything diferent, dunno what might be a true bolt-on. Keep us informed when you sort it out.