I have a 88 pickup reg cab with a bench seat that is completely shot I am having a hard time finding one but I have found several 4 runner bucket seats I am assuming these are pretty much bolt in? (maybe a little drilling etc.)

 

Well the seats should mount just fine. Not sure about the passenger seat since it is designed to slide up. The inside holes could just be covered. Easy way to find out is crawl under it and look for the nut that welded on the bottom of the body.