1941 Champion 400 S4G

I have identified my Champion as a 1941 400 S4G. I have registered this motor but it is good only for parts. I have acquired another S4G that runs and will register it also and it will be the motor I will use on my fishing boat. The manual says you are supposed to use 40 wt oil in regular or ethyl gasoline. In modern terms what kind of gas and oil can I use in this motor? I bought a pack of manuals to get the one I needed for the S4G. I have manuals for Champion Models 1941 2G,1941 3G, and 1942 1H Super-Single. If anyone needs any of these three manuals, I will send them to you for free.