Hiw difficult will it be to swap my 89 2x4 to a 4x4? I have a doner 88 truck for the parts

 

Welcome to the forum

Not an easy task
4x4s are built as 4x4s, its not an "option" added to a 2WD
The front frame is different between 2wd and 4x4s, there are no matching bolt holes to do the swap, you have to build the 2WD front frame to a 4x4 to add the front axle
And measure, measure, measure, then measure again, its very easy to f'up alignment

Front suspension seen here: https://therangerstation.com/tech_li...spension.shtml

Can be done, for sure, just not a bolt on type of project, welding will be required