Ok, I have a 88 truck with air, it has a somewhat new compressor that was on it when I got it. As far as I know, everything else is original I had it changed over to 135 and it will only get down to around 60 degrees, my question is should other parts have to be changed out to make it work on 135?

No other parts. What are the pressure readings.

Don't know, I had a shop do it. He does all of my cars, so I trust him.

Without pressures stated help is just guessing.

88 was still using R12. What compressor is it for. Also the oil for R12 is not compatible with R134. It may work but not a well as with the correct oil/refrigerant.

Yes, it should have R12 and they had already switched over to the rotary compressor in the early 80's. I don't know what brand the compressor is, just that it isn't original. I'm wondering if any of the other stuff like condenser has to be changed also.

When I convert these trucks I always replace the evaporator, condenser and drier. If the compressor is still good I remove it and drain all the oil, flush the lines then install the correct amount of PAG oil in the compressor. I also install two small 10" , 1000 CFM fans on the condenser. Getting good air flow across the condenser is key to making them cool and keeping the high pressure readings down with the amount of refrigerant I'm going to put in it. I vacuum it for a couple hours then charge it with 3 cans of r134a.