I've had many big singles, some with rev counters and some without.
I like to know what my engine is doing.
I rigged my phone as GPS speedo and went out with the rev counter showing on the XT Clocks.
I only collected two data points because I had to remember the figures on the fly.

GPS Speed Speedo Speed RPM
60 67 4200
70 77 4800

That's pretty good in my opinion and it'll be one reason the engines last so long. My car is turning at 3700 RPM at 70MPH so this bodes well as I expect my car to manage ~150,000 miles