When GM were working on the class 59, one of the early external design drawings presented to Foster Yeoman featured a loco that looks very similar to the IR 201 GM class loco. This was rejected by Foster Yeoman. Looks like the design was kept on file and presented IR when they went shopping to GM for the 201 class.
Will post a photo if anyone wants to see it.
From the book Foster Yeoman, The Rail Story. 75 years of aggregate by rail.By Colin J. Marsden.