In my opinion, all of the early "chicken little...the sky is falling" reports of Hell on Earth with the "improper" procedure, the reports are grossly over rated and basically are a really bad over reporting.
All you need to do in a properly functioning system is change from R12 to R134. Period.
I think it is a good idea to change the reciever /drier and switch over to the sankyo rotary compressor.
Other then that everything is fine.
What you will see in the difference between the two systems, R12 and R134, is that is is more difficult to get the temperature to blow out of the registers in the high thirty degree range.
The coolest I've been able to get is about 40 to 42 F out of the registers.
You will also notice that the 134 is a higher pressure system, but that's to be expected because R134 has different properties then the R12.
As FDR once said, "we have nothing to fear but fear itself".
You are going to get different opinions. Mostly from pencil neck engineers who just can read specifications and probably couldn't even install a hub cap themselves personally?
I'm sure they could supervise the heck out of the installing mechanic though?
On stuff like this one really needs to be a "hot rodder" looking for things that actually do work, but on paper don't?
I personally have found that the original Pantera system is on the hefty side and nothing fragile about it.
You can change the condenser but you don't need to. It's just needless expense.