Everyone I talk to always recommend Vintage Air first. I have yet to find anyone not happy with there system. I helped work on a Old Air system in a '55 Chevrolet car since I had the recovery machine at work. It was a black car with black interior and very little if any insulation. No amount of playing with gas volume or pressures could make the car cool on a hot day. We were lucky to get 10 to 15 degree drop from outside. I blame the unit and lack of insulation. I don't believe it was big enough even though it was a made to fit piece. Insulation would really help, but it still wasn't what I would consider cold air coming out of the vents. It did look nice and fit pretty well. Cooling of the condenser is a must, does your fan have plenty of air flow? At speed it won't be a problem, its the traffic jams that will over heat you. This is where high cfm fans come in handy.
If you have a bare cab, insulate the heck out of it, it will help even if you choose not to add air. Then, get the biggest system that will fit, even if you have to make it fit.
