Good score! The hole in the 126 grill is a PO mod, that should not be there. Who only knows what it was done for. Since it has a different exhaust on it and it is up too high for the PTO, I would say that the PO experimented with a custom exhaust pipe out the front of the cub. Who knows, it might have been a concept cub for the early Quietlines (QL), experimenting on the exhaust out the front.
I'm glad to hear that more cubs are being saved from the brush from your valiant efforts!
Cub Cadet 123