Hand Tools Archive
It should be quartered and pith centered when sawn (as in, you can follow a line along its length without having any grain runout in any direction).
The reason for that is if it's not centered, even if it's quartered, the plane will twist.
It would be better to have rift sawn beech that's pith centered along its length than quartered that's not. I wouldn't go so far as to recommend flat sawn, even though it might be OK, it'll be horribly ugly.
Cherry, Beech and hard maple are all fine - the former better than the last, and beech the best (cherry makes a light plane that dents pretty easily). The trick is finding them rift or quartered.
The only sure source I know of is horizon (their current stock is european):
It can take a while to get stuff from them sometimes, and it's not cheap, but compared to the people selling sawn billets online, it's not that expensive. They ship small quantities UPS, and two sticks would probably be about $135 shipped and would be enough wood to make a lot of pairs of planes depending on the thickness.