I would say, considering that George and Steve had to cast such a wide net, and found Quan by accident... there is only one. Sure, he was no oscar contender, but he had the energy and just the right amount of childishness to do what needed to be done in that role, in the specific film. And while there were plenty of child actors around, I can't think of any that were of Asian descent at that time. The role was a wild card, and so was the actor. Could another Asian kid done it? Sure. But I suspect, the choice would have been similar.
Actually, when I was in grade school, I knew a Korean kid who reminds me a lot of Shorty, in hindsight. He could have played the role, no problem. Are you out there, Steve?