I saw a master cylinder #5460346 that the person said it was off of a 68 with power disc brakes, it has a code stamped on a pad at the end of the cylinder FR. Is that the correct code and master cylinder?

1968 Firebird, not positive as I am no expert. Maybe someone more familiar with the '68 model will chime in.

5468309 is correct for a '68 'Velle, Nova, or Camaro.
BillL

If 5468309 is the correct master cylinder, can anybody tell me what the two letter code is that is stamped on the end for a chevelle?

I can't answer for a 68 but the code for 69 is BA.

IF the stamped code is supposed to be the code in the build sheet box, it could be CL (from a small block Elky) or IN (from a SS coupe) both Fremont build cars.
Wheelhop, is BA the code listed on the buildsheet?
BillL

The BA is not listed on the build sheet in 69. You would see CN on the 69 build sheet, which is the code for the whole unit, with the master and booster.