I have rebuilt most of my system.
Installed a parallel flow condenser.
Put r134a in it and saw temps of about 47F at the vent.
I didn't like that so I took the r134a out and put r12 in.
I use BVA Auto 100 from ackits which states the oil is compatible with both r134a and r12.

My 84 300SD says it holds 2.9lbs r12. I have less than that in there right now and I'm seeing high side pressures of well over 300psi. My low is around 25psi at.

Ambient air temp is 85F.
I am seeing 48F at the vent on the highway.

I took it for a drive with my gauges taped to the windshield and the high side needle was jumping all over the place.

I put 3 12 oz cans and started a fourth one. So I have somewhere around 40oz or about 2.5lbs.

Why are my pressures so high when I don't have a full fill?