A few notes that I forgot on previous posts. First, the pure-racing GR-4 & GT-4 cars used 1.25" thick one-piece rotors with aluminum 4-piston Girlings, and the racing rear calipers did not use e-brakes so bosses were not included on those caliper castings. There was no e-brake mount in the cabin, either and in fact the whole body was full of preformed sheet steel parts modified from stock stampings with large perforations added. They were done before the car was welded together- to make an accurate repo', you'd have to disassemble the car.
I think the DeTomaso Race Shop used seam-welding in many areas rather than production spot-welding, for more chassis stiffness. There was also no heater box/AC and the welded heater/AC mount brackets under the dash were never done on racers. The tabs for the lower front a-arm mounts were lowered by about 0.300" from factory and the entire racer used NO rubber in the suspension at all. There were many, many little tweeks on the GR-4s that were not found on Gr-3 or other production based Panteras. I once wrote an illustrated article for POCA based on Guy Trigaux and Les Gray's real GR-4s, that showed how one could tell a real Gr-4 from a clone, or as they now say- a 'tribute' car.
The Gr-3 production racers used iron 3-piston Girling calipers front and rear, with stock pair-of-pliers e-brakes. The uprights used very wide straight roller bearings at the inboard position. DeTomaso used to sell a complete kit of Gr-3 brakes and that's what I installed on one owner's car in the early '90s. When I say 'complete' I mean it: Everything including the front & rear uprights, bearings & spindles were included. Even dash-3 Aeroquip brake hoses and brake pads were in the kit! Everything cleared 8" & 10" Campagnolo wheels. Everything fit so it took me all day to mount & bleed the kit and rough-align the wheels. The next day he drove to an alignment shop. That car still exists in N CA- the owner is a POCA member.
The street based GT5/GT5-s brakes in the mid '80s were essentially the same as the early '70s Gr-3 brakes: all-iron 3-piston calipers and 1.25" wide 1-piece rotors. GT5 rears were from a Rolls-Royce, and the Rolls e-brake calipers were modified to clear slightly larger OD rear rotors used on DeTomasos (maybe front rotors? Dunno.) There's a long cross-bolt that passes very close to the rear of the GT-5 rotor. DeTomaso cold-bent a curve into that bolt for clearance. And being a hardened bolt, a number of them cracked in service. This modified bolt was frequently replaced on street GT-5/5s cars. I think someone began making an annealed version of the metric bolt that didn't crack.
As far as I know from the FIA Homologation papers, ONLY Girling calipers (aluminum or iron depending on class) were legal for International racing classes through the '70s. Later, after Panteras were obsolete, the door for brakes and other stuff was thrown wide open. The '91 ADA Pantera run at the last LeMans used a Hewland transaxle from one of Gurney's IMSA racers, and a Porsche suspension! If you're really serious about vintage-racing a modified Pantera and winning, check the current rules for the group you'll be dealing with. It likely will not look much like a classic Pantera! Not going that far, contact Anders Hellburg in Sweden on his Pantera Gr-3 website <www.scuderiadetomaso.se> He is still active (note time zone). I got an e-mail from Anders only a few days ago.