The 1970 Firebird in the listing photos looks perfect: fresh paint, straight panels, a Formula 400 hood that promises everything the second-generation Pontiac was famous for. But on these cars, the part that matters most is the one you can’t see from the curb. The front of the car rides on a bolt-on subframe, and everything behind it depends on a unibody floor and rear frame rails that have now been flexing, rusting, and getting patched for more than half a century. A car that’s gone soft in the middle will show it in sagging door gaps, cracked seams, and a chassis that twists every time you lean on the throttle. Before you fall in love with the paint, you need to know what’s holding it together, and this guide will help you avoid buying a beautiful body sitting on a tired structure.
