Get the piston on top dead center. On the AC version, ther is a mark on the prop drive hub that will correspond with a casting seam on the engine.

There is a mark on the cam that must be aligned with the pushrods.

Take the rocker arms off and raise the exhaust cam follower up out of the way so that you can seee the mark well.

Set the cam position and re-install the rocker arms.

You will need to adjust the valves. All the current four cycle engines use the same valve gap. It's about .002" -.004" which will get the job done except for a purest.