Mike,
Good information here. I can add a couple of historical notes. The 484 and the 488 were the two K-36's that did not receive the covers. I wonder if it may have something to do with the fact that from early 1951, when the K-36's were moved to Salida and the K-37's moved to Alamosa, the 484 and 488 were also left in Alamosa. Just a hunch, but I would guess these covers were being put on the locomotives in Salida in the late 40's and early 50's. Thus, the K-37's got them when they were assigned out of Salida, and then the K-36's got them when they went to Salida, but the 484 and 488 were left behind in Alamosa and never received them.
Also as to 483 having a different shorter cover, this is due to the fatal 1958 wreck when it rolled over outside Durango. The cab was rebuilt and 483 ended up with the short cover it has now. Before the wreck, it had a cover similar to the other 480's (those that had them).
Bill M.