Most ideas were shared already. I went through this a couple of years ago and IF all your front end components are in good shape and to your liking only then I would recommend to get into the springs. Moog in general makes a good and quality spring, still US made. I would get a strong spring for a big motor and AC, and most likely if installed correctly (I say that because of the positioning of the spring) your front end will be a tat low. Measure both sides to the wheel well and use a floor jack to put the front end were you like it. Then go here: http://www.globalwest.net/1105.html to order spring spacers to get the desired height. Spacers were actually installed from the factory to eliminate leaning. I have them installed on mine and am 100% pleased.
Got so hung up on the solid mounts, I forgot to add that. If you already like the ride, instead of replace, using a coil spacer to raise it would be a good alternative. Keep in mind, they are not linear (spacer height is not the same as how much it lifts the car) as noted in the Global West example. You could also check if there are adjustable ones to dial it in (this is just an example, contact the supplier to verify if they will fit in the Firebird). AdjustableHiddenSpacers
