First thing to do is a good exhaust, and a K&N air filter or the like in the stock airbox. A 3 inch single exhaust with the cats removed helps tremendously. Headers are a huge improvement over the exhaust manifolds, but finding them for the van chassis might be an issue. Put a 180 degree thermostat in. Bump your ignition timing up to 12-13 degrees initial from the 10 it's set at from the factory (you'll have to disconnect a tiny chip called the SPOUT connector from your wiring harness to set base timing accurately-it's not a big deal, just Google where it's located on your van and you'll find it) Bypassing the smog pump with a shorter drive belt and closing off the hose that connects to the exhaust system is an easy thing to do while you're doing the exhaust upgrade. Next is a fuel pressure regulator set to 40 psi-BBK makes them. Order one for a 95 Mustang with a 5.0. Do these and it'll make a different animal out of it. After this, there's camshafts that work with the computer, ported intakes, and bigger throttle bodies.