Mitch,
I converted mine to 134a without without changing anything besides the port valves, the receiver/dryer and the oil in the A6 compressor.
Positive:
Very easy, inexpensive, better for the environment and I can get it refilled if needed in any AC shop.
Negative:
The air is indeed not ice cold as it was whit R12, but adequate nevertheless (and I live in the Southern France where gets quite hot)
The AC hoses weep as the R134a molecule is smaller than the R12, but having said that, I did the conversion in 2009 and it’s still working fine without a refill.
R134a compatible hoses are available though.
If you want to do it the right way you should also change the expansion valve and this would give you better cooling.
Hope that helps,
Aristides