Whenever possible.. (some engines it don't work) I put the engine n the mount upside down so i don't have to reach arountd the exhaust port to mark the hole locations.

I generally mark one, drill it and bolt the engine on with that bolt... then mark one on the other side of the engne, remove the engine to drill... bolt it on with 2 bolts now....then do the last 2. With the engine bolted in place... less likely to slip while marking the next hole. (hate it when the engine slips and the holes end up 1/2 dia off from were they belong...)