I used methanol as a solvent with a air compressor powered flush gun.. Since you are replacing the Compressor, Drier, H Block, then flushing is a good way to go, because there could be debris in the lines. Also, replace all the o-rings and use nylog on them.
Make sure the expansion valve is disconnected as well. The expansion valve should be 134-a compatible.

When that is all done and reassembled, you will need to evac the system. But, pour your oil into various areas like the condensor, evap, drier, and the compressor. Make sure to turn the compressor by hand to cycle some of the oil, as you do not want a big slug of oil hitting the compressor.

 

Wow, great info, thanks a lot. I believe the expansion valve is part of the h-block, kind of a round looking thing????, not sure though . The kit comes with everything to do a conversion and this is the first replacement compressor that says nothing about r12 on it. The last one I bought had instructions for both. I went ahead and bought a flush kit, with a solvent that evaporates well. I have worked on ac before. I have installed a couple of add-on under-dash units, but this is the first conversion that I have done, again, thanks a million...Mark

 

Any time!!! Glad to help out!!!!

 

Well my freon recovery stuff came in and I got the system apart. I am converting to 134A, so I had new hoses made. I read that 134A will seep out of the old hoses, don't know if it's true. but after nearly 300k miles, they should be replaced anyway. I found my intermittent cycling, could not have broken off any closer to the clutch. Tomorrow, I am going to flush the evaporator and condenser and put her back together...Mark