And stock moby heads suck shit on hills. They heatsoak fast. At least mine did with a ripper cyl.
Go as big as you can if staying air cooled.
All this being said, I’ve seen some very stock moby 50v climb everything that was put in front of it, but it was very slow up them. Nate has one with only a cdi upgrade and a 15 that is surprisingly quick. But decent hill climbing and keeping up with cars is a different thing entirely