It would almost be easier[and cheaper] to find an 85-89 that has a bad engine with a good manual transmission. There's a lot of time and effort, not to say dollars, spent doing this kind of swap. You can do it, and will learn a lot, but is the education worth the time in this case? If it were me, I'd want to have two trucks, almost side by side, to be able to get that adapter or bolt without a trip to the yard, auto parts place or hardware store. It is very easy to blow through several weekends on a project like this if you don't have things lined up ahead of time.
tom