67 used a deep hole master w/ long pushrod, from what I can gather, and 68-9 used short pushrods/shallow master. Make sure you get a master which matches your pushrod.
Not sure, but I think the camaro used the deep ones all three years. 67-68 firebirds interchanged manual and power master cylinders, but were specific to the year because of the pushrod.
I think the PY master has ports on both sides, so if you want a generic looking (IMO) master that is made for disc/disc, get that one.
The replacement '67 master at most part stores will be a 70+ casting style single bail, unequal resivoir. The hole will be deep. If you are not after correct appearance, this master will work well. The equivallent with a shallow hole is for a 1970 Firebird with power disc. Use the one which matches your pushrod.
Most of the replacement dual bail masters will actually be disc/disc masters, having no residual valve for the rear drum brakes, and fluid displacement division for discs. Lots of people use them.
Another popular one is the taller dual bail 1.125" casting which was originally a pickup truck master cylinder.
Both of these are being redone as generic hotrod cylinders with ports on either side.
If you want the correct casting # for a 1968 Firebird, with a shallow hole, try Bendix R12121, Cardone 101731, or NAPA TSM101731. The picture shows their current stock to be the 5460346 cast which is correct for both 67&68 Firebirds. As far as internal displacement compatibility, I dont know, but it is a 1 1/8" master. The bleeder pads are there, but the bleeders remain uninstalled according to the picture. It will be a shallow hole/short pushrod style.
Whatever M/C you choose, check for the presence of a residual valve for your rear drums, and make sure it is compatible with your pushrod.
