I see this has been revitalized! Well since my post I purchased the Penn Central and the one I got has the open hole under the trucks. Then I bought the green one that had a repair station note stating that a truck had been repaired and this GG1 has one closed truck and one open truck! I suspect it originally had 2 closed trucks from what I hear. I can't imagine why one would require replacement. The repairman either had the truck in stock or ordered it from Lionel I guess we'll never know.
So I recently purchased a few trucks and will at correct the green GG1 so it has 2 closed trucks. Sheesh!
Happy Thanksgiving to all!
AL