It's an 89, his is the carbed 258. The biggest bang for your buck is to put a HO 4.0 head on it. Then, put a motorcraft 2100 carb (1.08 bore) on it, search google for "Nutter bypass" and follow the instructions, upgrade your ignition to TFI (a search will give you instructions), put headers on it, redo all grounds.
That should net you about 50 hp and make it much more responsive and smooth running. Depending on where you get the head from, and it's condition, this can all be done for 200-400 bucks.