Sanden compressor swap worth it?

I have a Kenworth with a York a/c compressor that just doesn't cool well. Compressor, expansion valve and dryer are all new and it made no difference. The sleeper unit is brand new and blows the same temp. For anyone who has done it before will swapping to a Sanden style compressor help with my temps any? I have gotten different answers and don't want to throw money away on a swap that doesn't help. Thanks,

Justin

 

This truck condenser is the one where it is the grille also (folds open with the hood, old w900a). They're wide open so nothing can even get stuck in them and it appears to be in pretty good shape. The previous owner supposedly cleaned the evaporator and resealed the duct work and everything else.
The truck does have heater valves on it that I keep closed. If they are open it won't blow anything except very hot air even if the a/c is on.
This weekend I was driving it and it was cloudy and in the low 80s and even with the fan on 60 degrees is as cold as it would blow. That was fine for that day but if the sun is out and it's up closer to 90 it's hard to keep the windows rolled up. That's with the sleeper unit running wide open and all the vents pointed at me.

Justin

 

I haven't thought to check that but that may be what's going on. Since I always keep the water shut anyway off I've never worried too much about it.

 

The sleeper unit is a complete brand new unit and it doesn't blow out any colder. It does share freon with the cab unit though which is what leads me to believe the problem isn't in the evaporator core but somewhere else.