I have a 68 firebird with drum brakes....I also have a 73 grand prix. Will the disc brakes from the 73 fit on the firebird? If so, what does this involve? Thanks - I am fairly new to the board and to my 68 firebird.

You can try it But I do believe they won't fit, the Firebird is a F body and the Grand Prix is a A body style,and they use different spindles, the Calipers probably will fit. Check a Scrap yard they have crossover books for parts.
There is a conversion kit, that's your best bet, it will have the correct spindles and rotors and Caliper mount.

Thanks Ragu - Where is the best place to get a disc conversion kit?

Ames performance, Classic Industries, Year One, Performance Years, anyone of these will have a conversion kit for your year and make.
I bought the the SSBC kit from Classic, I had to get it in a pinch, my drum brake anchor pin snapped off. You have the option to shop around, find what you want, any of these will have a economy kit to a brake performance kits. All work very well. Watch the clearence of the power booster with the engine.
I had to get a 9" so I could remove the valve covers, 68 maybe different
Ask others here which they recommend.

Thanks Ragu - I have a 68 that currently has a 350 in it (not original motor). I most likely will be switching to a 389 or a 400 so knowing clearances for the brake booster would definitely be helpful. Anyone else have any suggestions? Thanks!

I used these guys...

http://www.getdiscbrakes.com/

I used disk brake spindles from a 70 GTO along with the calipers and 2 piece 68 Firebird rotor. I believe the Grand Prix and GTO use the same front suspension with front steering versus the rear steer in our Firebirds. But I believe there was a change in the calipers in 73 to a one peice rather than the ones with the removable steering arm. If that is the case, the 73's wont work. The calipers and maybe the rotors are the same I'll bet.

Good luck

I have a cross-over list at home... somewhere. But the deal is to get the right spindle. And I know for a fact that the right spindle can come from a front steer car, you just need to use the rear steer arm from your drum brakes. It will work.

I bought a kit from Matt's Classic Bowties. Whole kit with master cylinder, spindles, rotors, calipers, hoses, prop valve, and all hardware for around $400.00. He uses parts from "The Right Stuff" which is quality items and of course I had some snags doing the conversion, but that's what this board is for as the information and responses I got were invaluable. I got my kit off Ebay. BTW, the difference in stopping is night and day from the 4 wheel drums!!!!