When you say 'no one converts the york,' do you mean that no one replaces the york with the R4, or the other way around?
Also curious, will the york handle the 134a? Is this what you mean by conversion?
Also, clarification on the 300D with r4...
checked with my mechanic, he replaced the motor in my '78 with one from an '81(?) 300D before he sold it. This would explain the R4 compressor and the unknown mileage.
76 240D - 545K miles
78 300D - 200K+ miles