Can a 1987 firebird fit formula engine?

No, a 1987 Firebird's chassis wasn't designed to accommodate a Formula engine without significant modifications. While both are Pontiac F-bodies, the "Formula" isn't a specific engine; it's a trim level that *could* have various engines, like the 305 or 350 V8, or even a V6. The issue is not necessarily the engine *itself*, but its installation and compatibility with the 1987 Firebird's existing mounts, wiring harness, and other components. You would need extensive fabrication and potentially custom parts to make it work. It's a major undertaking, far beyond a simple swap.