Well, my 1978 280z is finally on the road, the question that I have is, my ac works but it just doesnt cool enough, I put a thermometer on the vents and it reads at 55, and since its around 105 here in Texas, its just not cold enough. The question is how much r-12 freon goes in the original ac compressor. Or how much pressure should my ac gauge be at, at the lower side and the high side? Thanks.

Hold on. That's a 50 degree differential. You're not going to get much better than that without a bigger evaporator and blower motor.

The numbers are in the FSM, with service and test procedures. http://www.xenons30.com/reference.html