most civic engines are swappable in various models. you can easily do this swap...as SER said..get new engine mounts...but u dont need new springs at all. the 92-95 EG and then 96-00 EK series engines were aluminium alloy blocks and were not that heavy for you to need new suspension. Just make sure that your shocks are in good shape and u r good.
when u buy the engine...have it checked for sure. you should get an ECU, transmission (not sure u can use ur 90 Civic's tranny). I dont know if the 90 civic is OBD or OBD1..if that is the case..u will need upgraded wiring...
u must have a good mechanic to have a successful engine swap.