I don't like the idea of flipping the shafts for the reason Jerry explained, the hole on the bottom of the shaft provides the oil bearing for the rocker where the load is on the pivot. And then the two holes for lifter feed should stay where they need to be, which coincides with the feed in the rocker arm and it's pivot rotation. I don't really want to restrict the oil to the lifters in fear of them not staying pumped. Unless you shim them, then it most likely dont matter. Maybe tap the oil feed holes in the block. and insert a couple set screws with small holes in them, if you want to restrict the oil to the heads.
Personally, the oil in the heads don't bother me. My oil pan holds 12 qts and then the filter and lines. I will never run out of oil for the lower end if too much ends up in the heads. When I did take the valve covers off to inspect the valvetrain during the dyno sessions, there wasn't much oil resting in the heads. The drains appear to be very efficient.
