I am in the process of working on my 1945 70RC. The shop manual I have is dated  1951. It was bought at the museum in Charles City.
Under Section II, ENGINE, page 2-6; it states under ENGINE LUBRICATION the following:
Crankcase Capacity...  5 quarts
Oil Change Period:
HC Engines                  60 hours
KD Engines                  40 hours
Oil Pressure(late engines) 15Lbs./square inch.

I hope this helps.