A reground cam from www.deltacam.com
is a good perfomance boost, it'll only cost you about $60 after core charges, shipping. Lots of guys at ITOG have been using this cam and are very pleased with it; I ran one in my '86 2.3 and it worked well.
Calmini has a header for the 2.3 for around $190 or so (www.calmini.com
); Pacesetter makes one for the 2.6, but I don't know if they offer one for the 2.3.
Have a muffler shop install a hi-flow catalytic converter. At the same time, have them install a 2-1/4" diameter exhaust system from the cat back, along with a turbo muffler.
has real good deals on performance Weber Carb kits to fit the 2.3. With the cam and exhaust it'll run real sharp.
I was getting 24.5 MPG Hiway with my '86 2.3 5-speed, all it had was the Delta cam and upgraded exhaust; stock carb.
BTW, if you are reusing the stock head, be sure to have it inspected for cracks, and pressure checked for leaks. If it has problems, DO NOT weld repair it. Get an AMC head instead. If you look at the other posts here about rebuilds, there's some real good info.
If you are not boring out the engine to an oversize, be very sure to check the block carefully for wear/taper/out-of-roundness. These motors are real touchy on the quality of the cylinder finish; if you don't hone it out correctly it will use oil or wear out the rings prematurely. Best to have a machine shop hone the cylinders out with a diamond finish hone.
Check this out for some good info on the above: http://www.aftermarketworld.com/ar/ar49852.htm
Post here if you have any other questions, or at the ITOG board (you'll probably have a lot more responses there):