First, have the rear brakes "properly" adjusted. Then if the e-brake pedal is too low, you can crank up the tension on the cable. If you just crank the cable, the rear shoes will wear improperly. Most likely your rear shoes just need a little adjusting. You should have them cleaned and adjusted every 6,000 miles.
1997 F-150, 4.6, automatic, Dark Toreador Red, Supercab, Flareside, 4X4 Off-Road, Towing Package, Ford hvy dty rubber floor mats, Kenwood 10-disk cd changer, Ford bugshield, Chrome Grizzly Wrap Around Push Bar with 2 KC 100w Daylighters, Ventshades, Ford bedliner, cab and bed professionally undercoated, Code Alarm Sure Start RVS remote starter, Ford alarm, Realistic CB with Wilson Little Wil antenna and Astatic power mic, ported MAF sensor, and Lots of TLC!! (Besides being an F-150 nut, I am a Ford auto technician.)