At that particular point he is talking about the 956 and the 962. So not proof that the dials were lit in the 917. Driving the 917 on longer circuits and during longer events, getting the best out of the engine and fuel does mean keeping a close eye on the tach. The rev warning light comes on long past the point of optimum peak revs. Without dash lights I have to make a note of what objects I pass at the appropriate moment during daylight and then make sure I can see enough out of the side at night in order to time my gear shifts.