The best bang for the buck is to put a 4.0 head on your block. You can still use a carburetor, so it is an easy swap. You will gain 30 to 40 HP due to the better flow design of the 4.0 head. Fuel injection can easily be added later for a few more ponies, but it is a lot of work swapping sensors, computer, etc.
You should Nutter your ignition now (this allows removal of the computer) and install a pre-smog distributor to get the most out of what you now have, and will need this also after your head swap.
418 miles on 19 gallons of gas. Can't beat the BBD !