Re: quick question about 1984 s15 jimmy
2.8Ls are junk. They aren't worth the powder to blow them up. They don't even make good boat anchors. They're worth about $30 in scrap cast iron. They weigh a lot more, more expensive to fix, and don't make much more in the way of horsepower than a 2.5L.
For some reason, all 2.8L 700R4s I've ever seen have failed. I don't know why.
As far as rust, look all over the place for it. Rockers, front body mounts, core support mounts, front frame horns, rear of the box, front and rear wheelwells, under the rear seat.... the list goes on.