The readings depend on many factors, most of all ambient temp, so it's hard to give exact values.
Typically on a cycling clutch system I'd expect low side to be in the 30's to mid 40's idling on a moderate day (70F-80F). If the AC system is in good shape it will eventually drop the low side below the cut-off (around 20 PSI) and the compressor cycles off for a bit. The high side will be fairly high with R134a unless you switched to a modern parallel flow condensor. 250-300 PSI is normal. With a parallel flow condensor the high side will be right at 200 PSI. Makes a big difference.
You also want to look at how the low side cycles. If the pressure drops rapidly until the compressor goes off, then pressure comes back up and drops rapidly again, you're under charged. If the pressure is up in the 50's or higher and never comes down, plus the high side is over 300 PSI, you're over charged.
Typically on a cycling clutch system I'd expect low side to be in the 30's to mid 40's idling on a moderate day (70F-80F). If the AC system is in good shape it will eventually drop the low side below the cut-off (around 20 PSI) and the compressor cycles off for a bit. The high side will be fairly high with R134a unless you switched to a modern parallel flow condensor. 250-300 PSI is normal. With a parallel flow condensor the high side will be right at 200 PSI. Makes a big difference.
You also want to look at how the low side cycles. If the pressure drops rapidly until the compressor goes off, then pressure comes back up and drops rapidly again, you're under charged. If the pressure is up in the 50's or higher and never comes down, plus the high side is over 300 PSI, you're over charged.