[David Pozzi]

As you widen the tires, you increase the G forces the chassis will experience, stiffer springs are needed.
My wife has a 73 Camaro with Hotchkis TVS springs and anti-roll bars. If the car has Headers, lowering is usually limited in front due to ground clearance issues.

The wheels are Front 17X8, 4.5" bs, R 17X9.5 5.5"bs. TIRES F 245/45/17, R 285/40/17

You may be able to fit a 275 all around with slightly less backspace up front since it's a Firebird with round wheel openings. The 275 can fit up front on a Camaro but it hits the antiroll bar when turning sharply. If the turn stops are built up, the 275's will work on a Camaro I'm told, so they should fit a Firebird with the right backspace.
David