PVT has them, and Ron's Rocket parts.
As far as the long stroke and short stroke goes, a well built vanny just needs to get to its rpm as quick as it can, or cycle fast. The improved rod angle and extra long rods really help the upper rpm cylinder filling, also they are never in the rpm range where you would need the longer stroke. They aren't a real big engine but you sure can take advantage of what its good for.