Converted to R134a? If so, you would get better results from a parallel-flow condensor.
Better airflow involves making sure there are no leaks in the ducting, and a common spot for leakage is where the evaporator core lines exit the HVAC case under the hood. Also ensure the hot water shutoff valve is functioning, and the blend door is fully closing. I took the opportunity on a previous build to remove all the ducting (was replacing dash), clean it all well, added new foam to all the joints, and cleaned the HVAC case. Wife said it got too cold on the highway, I was fine with it, my only gripe was that the blower didn't spin as fast at idle as it did going down the road.
As an aside, it has been said that about the best you can hope for is a 50 degree reduction in heat with auto A/C...Another thing to consider is that in most climates, a portion of the cooling effect is the reduction of humidity. I would assume the air in Vegas is relatively dry, so that would perhaps lessen the perceived effectiveness of the system. I would imagine Vegas is getting pretty toasty by now...it's been 90+ here in "moderate" Oklahoma