Well for reliability, IMO I would recommend a builder that will not remove or thin the intake bridge too much (others have the bridge removed for a few years and still on the same piston).  My intake bridge broke when I overheated my piston the last trip out (wrong fuel burn down... my fault).  Make sure the builder/porter is familiar with the LT500, so they don't screw up the porting by making it too big and it hurts performance.

Good luck getting everything all setup.