In that case, i will look out for an 88-91 to make it easy.

 

To your question about motor mounts... Pretty much any 318 will bolt in using your mounts. Even with Magnum engines, (unused in Magnum applications), the casted mounting "ears" for LA style mounts will still be there. Obviously, with a Magnum swap, things such as fuel delivery get a little more complicated, but as far as bolting it in, that isnt an issue. Im running a Magnum in my '78/'85 hybrid.
If you are willing to part with it, I think the $1800 that the guy offered, in the condition that its in, is about as fair of a price as you could hope for. That being said, I hope you keep it.