You will find allot of interchangeability in Mitsu engines.

For an almost direct install get an imported 3.5 DOHC engine for about $1500. These are Diamante engines but will swap in.
You can install a later SOHC 24V engine, if you get one from a Montero it will go in with little fuss.
If the lower end of your truck survived the valve crash then just do the heads. Any post 93 DOHC head will do, the castings are the same. The 91&92 do not have the mount for the cam sensor.

Cheers, Charlie
If It ain't broke, Modify it!
87 Montero turbo Converted back in Spring1989
95 Montero SR 3.8 DOHC Only one?
93 Pajero 3 door 6G75 Mivec with paddle shifted 5 speed
Then a Gen2 SR with full coil independent suspension.