This engine has 2 counterweights in the crankcase. Does anyone know if they need to face the same direction, opposite directions, or what when re-assembling the engine? I don't see any marking on any of the gear teeth. Has anyone worked on one of these before?

See counter weights, part 758
http://www.briggsandstratton.com/ipl/pdfs/100/MS6796.pdf

i think they just go on, but its been a long time since i've worked on a vertical shaft syncro balanced engine. even though yours is a horizontal