As far as I know, most base Firebirds came with vinyl tops. Mine is a 71 base V8, and when I pulled mine off, I found out why. GM in their infinite wisdom didn't exactly do the best bondo job where the roof and the quarter meet up, so it was blatantly obvious from a smooth 10 feet away that it wasn't perfect. Now maybe when they started offering T-tops in 74 they were able to perfect that aspect, but I know on my car that I could have done better with bubblegum and Krylon, and my car had NEVER been repainted. Besides that, all my studs in the quarter panel and panel beneath the rear window were all pressed out holes (not drilled out) and the studs were the same color as the car with no break in the paint, which tells me it came with the top. What little rust I had in my car (California car) was not due to the top, but is the same old common rust areas that all 2nd gen birds have, except mine was not as bad as some of the cars I've seen from down here in the south.
