maximum milage project

[big10ratrod77]

so my dad bought my truck in 1977 with the intention of seeing how long it would last(the engine and drive train) well 200,000 miles later its mine and i dont like the crappy milage so ive been modding stuff open element air cleaner with K&N filter, duel exhaust(going on tomarow), and turbo mufflers. well heres the twist i cant go inside the engine(he wont let me) like cam, pistons, heads and intake cant be messed with, what are some tryed and true methods of more milage besides maitaince (its been well maintained). im thinkin 1.6 rockers roller tip rockers(thats as far as i can go inside the engine) for more lift to make it closer to a towing cam, and underdrive pulleys, whats some of yalls ideas