Yeah, I spoke to the state smog referee today who explained what I have to do.
It's legal for me to convert my 1989 Mitsubishi Mighty Max BUT I have to find a motor out of a vehicle that's 1989 or newer, it has to be a rear wheel drive vehicle (like my truck, it can't be out of a FWD vehicle), the vehicle has to be in the same weight class as my truck (no huge 10.654 liter diesel out of a Ford F9001 or a 4 cylinder turbo diesel out of a box truck). Finally, it has to have been sold in the US, not just North America.
So it's pretty stringent. This limits my choices to Mercedes only as far as I can tell unless I'm forgetting something. No Peugeot diesel for me!