On the houses/barn homes that I have been involved with or crew uses White Oak sills on top of a stone foundation. However we cut 10" wide (1/2' under the sill width) strips of Ice & Water that is stapled to the bottom of the sill. I should probobly mention that the floor system is temporary supported at its level and final resting place, then the masons finsh the last 1'or so of wall.
I great book Listing rot resistance is Bruce Hoadley's - Understanding Wood. A must read for understanding the properties of wood.
Two years ago I met a guy in western NY who replaced a sill with the wood the client had on his property - Black Cherry! New 30'+ 10"x10" hewn cherry sill - My kind of repair.
