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My two favorite easy bolt-ons that you will get a real "seat of the pants" benifit from is 1) MSD ignition, and 2) electric cooling fan.
I'd recommend the 6A ignition box, unless you have a DIS, then I'm not sure what to tell you, besides the Digital 6+ system. For cooling, you can get rid of your mechanical fan and go with a Permacool 16" electric fan, which will free up some power and extend the life of your water pump.
'77 F100, 302 (the aftermarket Prodigy), C4
Cadet Second Lieutenant John F. Daly III
South Carolina Corps of Cadets, The Citadel
The TorqueKing
You've improved on the intake and exhausting of airflow...I'd say it's time for a cam change to take advantage of the improvements you've already made. While your changing the cam you should replace your tim ing chain and gears, at 90K miles I'm sure you have a good deal of chain slop that's not letting you get to your full potential.
If you do not want to dig into the inards of the engine then a gear change may be in order depending on what ratio your running now. Deen