I just tried putting the conversion kit on my 76 300d. My hoses started spewing. Might be because they are old. The system had a leak before with r-12. I was planning on injecting dye to find them but instaed I have pulled all the hoses and plan to take them to a shop to be re-done. About $20 per hose. My mechanic buddy (20 years Catapillar) also sugggested that I replace the drier as the desicant has probably become saturated over the years and cannot be dried with heat. He said the local a/c hose shop could sell me a new one. He also recomended a system flush and vacuum pulled before refill. Your York compressor has a crankcase. The filler hole is on the left side. My shop manual has you make a dipstick out of wire to check this. Refil with 525 weight refidgerant oil avail at Autozone or others.