I think i have discovered my brake problems. It seems i have a long pushrod on my booster and a shallow bore master cylinder. The rod measures 4" and came with my new booster. I then bought a disc/drum master cylinder for a 72 chevelle, that needs a short rod. According to David Pozzi's great site,the short rod should be 2" 5/8.I was going to try and return the M/C and get one that takes a long rod.That would require finding the correct application to use. It will be easier to just cut down my rod to 2" 5/8 and use the chevelle M/C. It that ok to do? :confused:

Yes, I'd cut the rod. Booster rebuilders may have the shorter version, but I don't see any problem with cutting yours, it just pulls out, if you haven't removed it yet.
David

Check ClassicIndustries Part # PBK10

I cant find that part# on classic's site.? Is it a shorter rod?

If you opt for a different master, the one listed for a disc brake 1967 Firebird or 1967 Chevelle has a deep hole and is a 1 1/8" disc/drum master.
67 Chevelle also lists a separate one for manual brakes, which I believe to also be a 1 1/8" deep hole.

Its in the downloadable catalog, it shows as a new item Its actually a kit that includes both rods, here is the text from the catalog

"Power Brake Booster Kit
This kit will come in handy when re-building your master cylinder and power
booster on your power brake system. This kit includes the plastic sleeve (boot), two
push pins (one for a manual m/c,one for a power brake m/c) and the attaching clevis.
PBK10 1967-69 .................................................. .................... 18.95 set"