Will a 1999 GL1500 engine fit into 1994 chassis?

No, a 1999 GL1500 engine will not fit into a 1994 chassis. The 1999 GL1500 engine is a fuel-injected engine, while the 1994 GL1500 engine is a carbureted engine. The fuel injection system on the 1999 engine requires a different fuel pump, fuel lines, and injectors than the carbureted engine on the 1994 model. Additionally, the 1999 engine has a different ignition system than the 1994 engine, so the wiring harness and ECU would also need to be changed.