Well, just replaced all the components on my system due to a compressor locking up. Replaced Condenser, Compressor ( new AC Delco this time!), accumulator and orfice. Flushed the evaporator and the lines. Relpaced all the orings with Green ones. Used 8 oz. PAG 150 oil. Put 1/2 in compressor, other half in accumulator. Compressor had no oil in it from factory. Allowed compressor to sit face down for 30 minutes for oil to coat front seal. Installed compressor, then rotated by hand 10 revolutions to move oil through compressor. Evacuated system to 29" for 45 minutes. Vacumn held after sitting for 45 minutes, so began charging process. Started engine and manually cycles the clutch 10 times to burnish the clutch ( per instructions). Charged with 43 Oz of R134.

Everything seems to be working OK. Vent temps were getting too low ( 32), and the compressor was not cycling much, so I adjusted the Low Pressure switch so that the compressor cycles. Vent temps came up to 38-40. When reading the low pressure guage, compresser cycles off at about 22, guage climbs to about 45-50, and the compressor cycles back on. High side pressures were reading 150-160. Ambient air temp was 75.

My worries. Cycles now occur about every 45 seconds. When the pressure is approaching the low side ( 22) feels like the compressor is straining, and you can feel the vibrations in the car. As soon as the compressor cycles off, vibtrations subside. Any thoughts? For info, I am running a serpentine setup with TPI, and have no additional braces on the compressor other than the three bolts that hold it to the AC bracket.

It looks like you did everything right. 45 seconds cycle time with good vent temps isn't bad.
However, you may be just a bit undercharged. You want to measure the ambient temp just in front of the condenser and aim for a high side pressure about 2.5 times that number.

2.5*75=187.5, so you would want to see about 190psi. Thats with the engine at 1500rpm, MAX AC setting, High Blower and the doors open.

Thanks for the response. After some research online, I think the low pressures at 21-22 were too low, so I moved them up to 25. Compressor seems a lot happier. Cycling was pretty quick, so I added another 6 oz. Pressures still look good, and I'm getting 38-40 at the vent ( 95 ambient). High side was at 2.2 times ambient. Cycles now with 12 sec on and 5 sec off.

Should I add more to get the cycle times longer and the High Pressure higher, or should I just say good for now, and wait to see how it handles 105 ambient?

38-40 at 95 ambient on a converted system is pretty good. See what it does over 100F.
The cycle times seem a bit fast though. I wouldn't expect much cycling at that ambient temp. (I'm wondering if the switch is a bit flaky?) If the High side was at about 240, I wouldn't add more.
If you have access to a digital, contact type thermometer (a big if, I know) you could measure the temp of the evaporator inlet and outlet lines. At optimum charge, they will be equal, within ~5 degrees.

If the evaporator didn't ice up with the low side at 22 psi, it would be ok to leave it there.

I have a thermprobe for my mutli-meter. I'll try that tomorrow. Measuring with a handheld laser thermometer, temps were pretty close- within 5 degrees for sure. I wouild like it to cycle longer, but the compresser really starts to grumble when it gets down to 22. Whole car vibrates, and it sounds like it is going to tear itself apart. On cycling, it rapidly goes from 25 to 42, and then the compressor kicks in. It doesn't take long for it to get back to 25. I suppose I could go down to 24- maybe even 23, and see how it reacts. When I had it intially going down to 22-21, I was getting 32 at the vents!

Adding a few extra ounces of R134 gained a few seconds on the cycle time, but I'm afraid to add more until I see how it handles the 100+ temps. Besides, it's cooling pretty good- 38-40 vent temps yesterday at 95 ambient, with my new Auto HVAC controller set at 68.