The UO-8s that Bicycle Exchange sole in 1967 came 52-36 x 14-26. My friends bought these. I had my FW swapped to a 28 and destroyed several derailleurs. Granted my bike was not very well serviced but it was also obvious that I was pushing the physical limits of the plastic bodied derailleur with my setup. I would strongly advise going to narrower gearing if you choose to go Simplex unless there is concrete evidence that the later Simplexes were of a different geometry or construction.

Ben