AC retrofit to R134A

[70 gmc c2500]

My son recently picked up a 70 GMC C2500 with factory AC that wasn't functioning when he bought it. Someone in the past replaced the compressor with an aluminum 10 cylinder compressor that replaces the cast iron, 6 cylinder axial A6 style and installed R134A fittings but apparently nothing else. From my understanding I need to replace the condenser, receiver/drier, expansion valve and do a POA conversion? With that being said I took a look at oldairproducts.com and found those components...

50-2551A POA update kit
25-0057 Expansion valve
51-7211 Superkool condenser kit

Would these be the correct parts needed?

I also understand that the evaporator and the compressor will need to be properly flushed and then once all the new parts are installed the system will need to be vacuumed down and then proper oil and amount installed and the system charged back up with the proper amount of R134A. Am I missing anything or have I got it under control?