I have a 1989 F150 ,302,AOD 171000 miles with theses mods...Jacobs Milage master with ceramic boots and DEI boot protectors,K&N,edelbrock ceramic headers, Gibson 3" Stainless cat back system,cold air intake box(came stock on F250's as i recall).
Not sure how to add photos to this post but uploaded some photos some where.........
How about doing a head upgrade,rocker arms?
I was thinking of 'Power heads" http://www.powerheads.com/SB50.html or AFR 165 heads.
Also i think the 1989 F150 came with hydralic flat tappet cam(not the roller cam) and bank to bank injection and not sequential electronic fuel injection system.................