In early paperwork from late 17 and early 18 it would make sense they might stick with what’s familiar in regards to nomenclature. With the durability changes like the axle, axle shafts, ring & pinion, and bearings you’d think that wouldn’t be the case. For sure, if one was ordering parts, you can’t just say D30 or D35 for axles, bearings, & axle shafts for them. I think the R&P might be interchangeable though. At minimum, they say JL D30 and D35 on Spicer parts pdf’s etc.Uhh, Dana would disagree with you.