Here’s a curious thing, though. The book “Alco Official Color Photography” (*) has a very small section (disproportionately small in my view) section devoted to export locomotives. The second example shown was the DL541, of which it was said: “This model was offered from meter gauge up with a choice of two three-axle, three-motor trucks or a 1 C-C 1 four axle arrangement for light rail”.
That is the only mention I have ever seen of a four axle option for the DL541. Nothing similar was mentioned in respect of the DL543, but in that case the commentary was specific to the PER example shown. The DL541 picture was of one for Chile, but part of the associated commentary was general in nature.
Given that this book was based essentially upon Alco original materials, there would seem to be little doubt about the veracity of the statement about the 1-C-C-1 option for the DL541. It was almost certainly drawn from an Alco document or drawing. So the inference is that following “The Pony Truck” affair, someone in Alco decided that there ought to be a 1-C-C-1 option for the DL541 (released in 1960), which was Alco’s nearest match to the GE U18C. I’d guess too that Alco specified the GSC 1-C truck. But in the event, nonesuch were built.
The market for CM gauge diesel-electric locomotives with the 1-C-C-1 wheel arrangement turned out to be an entirely African one, sub-Saharan at that, and spanning the period 1955 through 1978. Of the total of 334, English Electric built 95, GE built 125 (all for SAR), Hitachi built 12 and MLW built 104 (all in the 1970s, and including the last of the kind).
Alco probably did bid – unsuccessfully - on subsequent SAR business. SAR started building up a large fleet of the GE U20C model, with standard C-C running gear, from 1965. At this site: http://alcoworld.railfan.net/export.htm
" onclick="window.open(this.href);return false;, the “DL543SA” is mentioned as a proposed modified DL543 for SAR, presumably somewhat lighter than standard to meet the SAR axle-loading requirement (around 34 000 lb) for operation on the Eastern Cape lines, which is where the early U20C fleet was used.
(*) Walter A. Appel, “Alco Official Color Photography”, Morning Sun; 1998; ISBN 1-58248-006-0.