I have a 94 dx 4dr and I want to change the motor it's a 1.5 single now. What kind of motors will fit & install easily?

You can stuff most of them in there with the right adapter kits and wiring... with the exception of the S2000 engine.

You have to define easy. Seriously. And what are the results you are after. Power and speed, straight line acceleration or handling or fuel economy? Every engine has its strengths and weaknesses depending on what you are trying to achieve.