Correct way to recharge AC 72 Duster 340 with Sanden 508 compressor

I would not re-use the hoses nor receiver dryer. Flush the evap and compressor and make certain you get all old oil out. I guess what I'd do is use trichlorethylene same stuff in brake clean, then flush with R-134

If you need pressure for the trich, I'd use CO2 or nitrogen, then blow both out with only the CO2 or nitrogen, then waste a can each of 134 for the evap and the compressor

Immediately seal it up and evacuate, then purge with yet another can of 134. You can purge into the high side fitting when under a vacuum, the 134 will travel through the hoses, evap, and back around to the compressor. Add nitrogen or CO2 as necessary to pressure test, then evacuate once more and re charge.

Many guys have argued with me on this, but a great way to get the new charge started with less fuss, and completely safe, is to start with the evacuated system, dump LIQUID refrigerant into the HIGH side fitting. By the time it is around the backside to the compressor, it will have flashed to vapor

Do what you can to keep the evap warm when evacuating and starting to charge. Do this on a warm day, and use the heater if necessary to get the interior up to at least 80F

Also when evacuating it is a good idea to warm up the engine and engine bay. Keeping the AC system warm will help to vaporize any remaining moisture and carry it off with the evac