[Odaroloc]

Im no expert by any means as i am only 16 but I am learning and really want one of these old trucks! Does it have an inline fuel filter? We recently moved from Kansas to Alaska and our RV has a 1983 454 in it and it was doing the same thing. Only got to about 40 then started to die. We replaced the inline fuel filter about 7-9 times and found out that there is a lot of rust in the gas tank and the filter was getting clogged. Once we replaced it, it was fine for a few hundred miles and we could get up to 70-75 and then it would clog up again and we would be back down to 40. Not sure if this helps or not but i figured it couldn't hurt. Hope you find the problem.

Mike