I am looking for a good rebuildable original master cylinder for a 1968 Firebird with power drum brakes. Can anyone confirm that the correct casting is 5460465 with a CT code?

After a couple decades of using an aftermarket master cylinder, it is pumping fluid from the primary to secondary side and leaking out the back. Rather than rebuild the aftermarket one or buy another aftermarket replacement, I may finally get the numbers correct part back on my car.