87 D150 Computer question
 

Hello all, I have aquired my grandfather's cherry 1987 Ram 150 2WD truck not a spot of rust. It has over 100K but only 20K on the rebuilt 318 motor. It is the 3 speed auto. I'm going to use it for a weekend truck and to pull my 3500 lb. two horse trailer. I've noticed that, although it runs great when not pulling, it lacks power when you get over 65mph. I was wondering if there was a way to reprogram the computer for the higher speed limits and change the power curve. I would bet that at 65+, I'm on the back side of the power curve. At 55-60, it pulls fine. Any suggestions?