A/C problem

I've got a 1990 buick lesabre. I retrofitted the A/C system to the R134a refrigerant after fixing a leak. I removed the compressor, drained the oil, put in r134a compatable oil, replaced the receiver/dryer and charged with 80% of the r12 capacity. I'm only getting lukewarm air from the vents, about 52 degrees or so. I like ice cold a/c; is there anything i can do to improve the cooling, or could i have messed something up that toasted the compressor? The high side was reading 200 psi and the low side 30psi at 80 degrees ambient temp. When i charged the system, i inverted the refrigerant cans (sent it in as a liquid instead of a gas to the low side) to get it to charge faster? could this have damaged something? thnx for the help

R-134a is not as cold as R-12. A 30 degree temp drop on R-134a is a good temp. 52 sounds pretty good.