You're right in that without the VIN you can't tell much beyond what you've described, as far as what the car was originally. If you get the chance, you can get the cowl tag information (separate from the VIN tag) and that will tell you what the interior and exterior colors were originally. Once you have the VIN you can contact Pontiac Historical Services (PHS) and they can get you a copy of the car's original dealer invoice, which will tell all there is to know.
All Firebirds made after the 1974 model year were single exhaust. The pipes from both exhaust manifolds went into a "Y" through a single catalytic converter. The W72 option cars had pipes that came out of the converter and split through 2 separate resonators, then up over the axle and out the back. The rest of the cars ran a single pipe out of the converter, up over the axle, and into a transverse mounted muffler, which had 2 pipes that came out for the right and left sides. There were no true dual exhausts and the cars never had 2 converters -- only 1 converter, and it was a pretty restrictive exhaust system.
All TAs got front and rear sway bars.
You need to understand that during this time, power/performance was actually NOT the top item on the list for the car makers. For them, meeting the EPA emissions requirements was #1. If they didn't do that, they couldn't sell ANY cars. The second consideration was fuel economy, as it was an important factor after the 73-74 gas crisis and the EPA was looking at Corporate Average Fuel Economy (CAFE) for the first time. Power/performance was consideration #3, and customers were willing to take what they got because Pontiac promised more than anybody else did with comparably priced cars at the time. But all of the engines were rated at less than 220 HP (W72) and the other engines maxed out at around 185-200 HP. Your average pickup truck has more HP today than the "hot" cars did then.
For $1,000, it doesn't sound bad, though, provided it hasn't been eaten up with rust -- particularly in the rear frame rails. You really need to take a hard look at those, which means getting under it, because those CAN be a deal-breaker.
Good luck!
