I measured across hole centers and it looks like I have the common 116 BCD, 3 arm crankset. It would be nice to simply swap the 52-42 for a 52-38 or something. I just upgraded the derailleurs from the worn out Simplex to a nice set of Huret Challengers and I'd hate to spend yet more money on different derailleurs..
Although as discussed elsewhere, the Dawes frame will do, size-wise, It was a cheap-bike first attempt at fixing up a vintage 10-speed and not in the best shape cosmetically so I'd hate to put good money after bad. I was thinking I could keep it for flatter terrain and buy a slightly more modern, yet vintage bike with cotterless crankset that is more readily upgraded.