Gears are incredible, go with gears all the way! A new cam, pushrods and rockers arms would be an excellent mod choice as well, but price for price and as a basis for other mods, gears I think would give you the biggest bang for your buck.
------------------
previous name: 84stangLX
'84 Mustang 5.0 LX
my LX
'89 Mustang GT
my GT