[plug ugly]

I found a parts truck F350 and a 250, both with the 351 and ZF. Obviously i can rebuild the motor to go into my 94, the ZF would work, but would the computer work, and is there any smog issues with using that motor that would prevent california smog from passing it?

 

[RLKBOB]

All your 94 accessories and smog stuff from your 94 will bolt right up to the 90 engine no problem so the smog shop wouldn't even know it's not the original engine. As long as it's all in proper working order then you're good to go. Assuming you have an E4OD trans the computer will work but you will have at least a couple stored codes. They won't affect driveability and I don't think the CEL will be on but if they pull codes as part of the smog test then they might fail you even if the codes apply anymore(b/c of the lack of the E4OD). I don't know if they pull codes on you or just make sure the CEL isn't on but this should answer your question.