@GregM posted:While looking at photos of Conrail RS3 engines, I came across this one;
Conrail 9961 Altoona, PA. 08/051984
The “shortened hood” is an interesting feature.
Was this a factory option or a common modification?
That's a shop modification, not an option from Alco. Note the twin stacks on the long hood. The original Alco prime mover and electrical equipment have also been replaced by an EMD prime mover and EMD electrics. Some of these modifications were done by Conrail and some were done by Penn Central. The locomotives were classed RS3m.
EDIT - Looks like Jonathan is a faster typist than I am!