No real recommendations..
On my 91 Bonneville LE I used the Retrofit kit in 2000... I added the R134a and the Ester oil which is compatible with the R12 Oil... I then charged the system to 85% capacity with 134a... With 134a you use a bit less as compared to the R12, I think thats due to the added oil..
My 91 After 8 years still cools and does it pretty well for a 17 year old compressor slowly working to its deathbed.. When I first charged the system with R134a it actually cooled really well sitting still on a 90F summer day.... It doesn't work as good as it used to..
I think the right way would at the very least would be to replace the Orifice Filter( Inline ) and the Receiver / Drier as well as the system O rings as the system would be apart.... From there being that the system has been opened it would be advisable to pump the system down and then recharge with 134a..
Too bad I have no experience with the Freeze 12 tho... wish I could be of more help there..
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