I just had a kit installed (289 w/disc brakes) that I ordered from speedway motors because even with the discs, it took gorilla power to stop the car (literally unsafe). Speedway was the only source I could find. I don't know about differences between the 6 and 8. I suggest you call them and get a tech on the line. Even though mine worked out, a couple of mods were necessary. I had bought one from Advance first and it didn't come close to working. I was told that older Mustang ll's and Granada's can work, but I don't know that for sure...plus they're probably all gone from salvage yards. Good luck.i have a 1966 mustang coupe 6 cyl. 200 cubic inch engine
and i was wondering where can i buy a brake booster specfically for this car? or put one from a newer car that may work?