BTW it is a Classic Auto Air system.

I don't have that data presently. I am more worried about total 134a wt. I just looked on a mid-90' Suburban (1500) with rear air and the chart shows 64 ozs. Does that sound plausible? I picked that model because of the length of the vehicle and distance between front and rear evaporators.

I've installed a front and rear a/c unit in an old, 6 cyl. limousine that never had ac before. I configured it as I found info in the ariazone AC manual. I'll try to post a photo of the system. There are 2 cut off switches installed so that there could be front or rear...or both ac evaporators worki...