Will a 1985 camaro engine fit in 1992 Mercury Grand Marquis?

No, a 1985 Camaro engine will not fit in a 1992 Mercury Grand Marquis without significant, and likely impractical, modifications. The engine bays are completely different sizes and designs. The Camaro typically used smaller, more compact V6 or V8 engines, while the Grand Marquis used much larger, typically front-mounted V8s. Even if you could physically cram the engine in, you'd face insurmountable problems with mounting, exhaust, wiring harness, and transmission compatibility.