tnporsche,
I just did this back in July. When you say "new compressor" are you talking about a factory rebuilt compressor or new retrofit like Kuehl or Sandeen? I installed a new Kuehl compressor and it came loaded with the correct oil. Make sure you know how much oil comes in the new compressor if you are going to add oil with the charge or you will coat the condenser and evaporator with too much oil. I had to drain and measure the oil in my new compressor in order to know exactly how much oil it came with. I too used Freeze12 and I am satisfied with the results, although I don't think it performs as well as R12.
Here is a link to a Freeze12 conversion chart that will tell you the correct pressure readings. I used about 2 and 1/2, 12Oz cans which is approx 90% of the original 33Oz charge for the system.
http://www.freeze12.com/techsup.htm. With Freeze12 you will still see some bubbles in the sight glass when the system is charged correctly, that is normal. If charging with R12there should not be any bubbles.
I also recommend removing the expansion valve and flushing the entire system (lines, condenser, evaporator) with a good AC flush, then install a new expansion valve.
By the way, it's like in the teens right now in the deep South. You really need that AC right now?
Good Luck!