1990 3.9L Motor Swap

Okay, I have a 1990 Dodge Dakota 3.9L and wanted to swap to the same motor to make the change easy and efficient as possible. What years will work for this change, because I know they changed motor types soon after this year. I would like an entire list of years before and after 1990 that would make for a direct swap using everything else other than the motor itself.

Oh yeah and if you have any idea as to where I can find a motor that would fit this description for cheap whether its in a wrecked truck or whatever, I live in upstate New York south of Syracuse.

Anywhere from 1987 to 1993 model years should work fine.