Great! That resolves it. DS-4-4-660 must have been configured with 4 stacks on some, and 3 stacks on others. I was perplexed by Jeff Wilson’s book, Model Railroader’s Guide to Diesel Locomotives, which has a photo of Norfolk Southern #662. The caption says it’s a NS-4-4-660 and has 4 exhaust Stacks... my photo of this, below, is pretty poor, but you’ll see what I mean about the stacks. — Ken
