"...74 to 76 Firebird Esprit.."
Everybody always has opinions about what others should want.
So, here's my opinion.
LOVE the idea of a real potent "Sleeper". With the Pontiac parts now available, a 12 or even 11 sec Esprit sleeper is definitely possible.
Of the years you mentioned, I'd MUCH prefer a '76 model. Because: The '74 & '75 had strange lookin front & rear bumpers. For '76, the front & rear were changed. Looked much better, IMO.
A mild pump gas 455 should push a '76 to high 12's, if the car will hook up to the pavement.
Then, obviously, more serious big cube engines could run quicker. And there are street legal soft compound tires now, if needed, for special occasions.
Here's a former Indy class winner, which was a base '76 Bird. Remove the stickers & change to plain lookin wheels/tires & it wouldn't look quick, at all.