As far as I know, there is no drop in engine from the later EFI Broncos. The engine mounts and transmission bell housing it has are not for the small block engines in the later Broncos. You are probably leaning toward any EFI 302 or 351 plus transmission, including the computer, engine harness to go with it, and mounts. Also, gas tank and high pressure fuel pump. The 85 t0 92 had two fuel pumps and then they switched to a HP pump in the tank.
Some of the other guys on here can direct you to places that sell some of the hardware you would need and give you a more complete picture of what is needed to do the conversion.