[Steeveedee]

If you have a sight glass, I suspect that the receiver/dryer may not have been changed out for one compatible with R-134. Can you post a picture of it? Also, the AC depends to some extent on ram air flow. When I work on AC systems and the pressures go up, I put a box fan in front of the radiator to increase air flow. This will drive the high side pressure lower. In a pickup, the evaporator being small isn't necessarily a bad thing, since the cab is so small, so the efficiency issue is reduced.