Jeep Overheating with A/C On

I got a 2008 Jeep Wrangler with the 3.8 that overheats when the A/C is on. It seems to only happen at higher speeds (50mph and up). It's got a brand new engine in it as the old one had a cracked head. This problem happened with the old engine too.

My coolant level is good, the fan is running, the radiator is almost brand new, and got a new water pump with the new engine.

Should I go ahead and replace the AC compressor or doe you guys have any other suggestions?