Q: A/C pressure is high on both sides after compressor, condenser, accumulator, orifice change

After changing the compressor, condenser, accumulator/drier, orifice tube and the rear expansion valve the mechanic says that both the low side and the high side pressures are too high. It does have the rear AC with separate controls for that.

He says the low is 80 and high is 375 and will go to 450. Granted it is 100 degrees here in Arizona. He swears the proper amount of oil and refrigerant is in there and thinks that the front evaporator must be plugged internally. It does blow some cool air from the front and cooler air from the rear AC. Any ideas?

Also before this the AC would blow slightly cool but was low on refrigerant and compressor was going bad. Also someone before we owned the car had worked on the AC it looks like as well as the rear AC since an access hole had been cut in the rear to get at the expansion valve it looks like.

My car has 187000 miles.
My car has an automatic transmission.