I'm in MN so that rust thing is a problem here too but my donor parts seem solid enough although not rust free.
The original buckets were out of a Chrysler Sebring. Grabbed them because of the integrated shoulder belts. Currently I have a 90s Dakota bench seat sitting in the truck. It seems to fit very well and I'm leaning towards using it and just figuring out my own shoulder belts. The bench seat also fits the look of the truck better to me. I'm trying to go for something that looks old to the point I'm considering a 12v generator over the alternator