Not getting desired vent temps after Sanden conversion

[cbjukraine]

I'm running the stock condenser with R12 and saw only about 48 degrees at the vent today on the freeway @60 mph. I stuck my digital thermometer out the window and measured 92 degrees ambient.

I just checked the pressures:

@ idle (with aux fan on)
high side: ~225 psi
low side: fluctuating between 45 and 55 psi

revving to ~2000 RPM
high side: doesn't go higher than 250 psi
low side: doesn't go lower than 30 psi

I've also leak checked the whole system with a halogen sniffer and go no alarms. Any help is greatly appreciated. I want ice cubes blowing out of the vents! This is very confusing, as two summers ago I had a stock working system with R12 and was regularly getting 36 degrees in high 90s Texas heat.

I'm referring to the car in my signature...