Does anyone know who manufactured the train for the Gatorland Express in Florida?

Are you talking about the original or the replacement? The original came in 1965, but it was replaced in 2001 with a new one. I was just down there and rode the new one. They also still have the original locomotive on display.

the original train was an Allen Hershell Iron Horse 4-4-0, its currently on display. The new train appears to be a custom fabricators 0-4-4 steam outline.