Amen to that,

I have done many conversions, and I never use the adapters for the line hoses, because my manifold set is old. I just put the low side adapter in the center of my manifold so that I can get proper pressures instead using the sight glass technique. (I own all of these cars, and never sell them) You definitely don't want to add freon for trouble shooting until you know for sure. On the other hand, if the system is already open, or if you are going to be opening the system, changing the compressor or cores etc, you will need to change the drier, flush, vacuum, reoil, and recharge anyways, so you can make the choice at that time what refigerant to use.