There's a psychological lesson here, too! Both of us have read that "Extra 2200 South" article repeatedly… but, now that the question about traction motors is at the front of our minds, we notice things in it that we don't remember from our previous readings! Thanks for rereading… again!
So, it would seem that the 726F was used from 1942 through the end of WW II. The 726C was used in (at least some) 1940-built HH-1000. I've been trying to think what ELSE GE might have supplied 726 motors for direct search efforts for the other 726 subtypes: I've posted a query to the GE forum about the large centre-cab switchers what GE built for people like the Ford Motor Company and the Monongahela Connecting Railway...
Re: weights. GM&O and Southern units, given their gear ratios, would have had 730 motors. These are probably a BIT lighter in weight than 726 motors (As "Typewriters" pointed out in an earlier discussion of traction motors, the 726 seems to have been a bit more "forgiving" in its short time ratings than the 730, and I suspect this means more copper!), but not by anywhere near enough to account for all of the difference. Notice that the Southern's earlier units were built about the same time as the Santa Fe's pair, but don't match them exactly in weight.
(Thought: The New Haven is in the Northeast, the Santa Fe goes over the Rockies, but the Southern is in the South, and the GM&O was too (it didn't take over the Alton until after WW II, I think). So maybe Santa Fe and New Haven thought they had to support greater steam heating efforts, and had, if not larger steam generators, larger boiler water tanks? (NB: this is a GUESS!!!))
Note that in the Santa Fe pair (built 1941) and the Southern's earlier -- 1941 -- units, the B-unit is actually heavier than the A unit. (Puzzling, this… unless maybe the B-unit had extra water tankage?) In the Southern's later pair -- built in 1942 around the same time as the New Haven's first order -- the A-unit is significantly heavier than the B-unit. So -- this is another GUESS -- maybe some time in mid-late 1941 Alco decided -- maybe to improve tracking, maybe to reduce costs by using cheaper materials -- to change to a heavier structure for the cab and nose end of the unit?
The first New Haven order were lighter than later ones. Given the dates, I am sticking (until someone comes up with actual documentation to show otherwise) to my guess that this is a matter of heavier car-body structure: giving up on some of the earlier efforts at weight saving, either because of cost or because it involved materials hard to come by in war time. … Given that the New Haven was using the locomotives in dual service, they probably didn't mind a few extra thousand pounds for better traction on the hills of the Maybrook route.
Thanks again for making these efforts, and posting the results. Tastes doubtless differ, but ***I*** find the minutiae of technical development fascinating!