Testing a car engine for performance should be done on an inertia dyno. It's the quickest way to get a curve through the entire RPM range. A prop will only give data for one speed. Do the math and make sure your flywheel is safe at the speed you want to run it. The clutch will not disengage until RPM drops below engagement speed. This is a simple fact of life with a centrifugal clutch. You can use a one way bearing to allow the flywheel to overrun, or put a brake on the flywheel and use it, to prevent the engine from being run so fast with the throttle closed(read no oil flow). Props can be used, but then you're talking many test runs to generate a curve. Who uses a dyno? Mostly the engine tuners. Google and youtube turn up plenty of information about inertia dynos. An inertia dyno needs some electronics to get the data. At the bare minimum a rev counter with a timer, the rest can be done by hand.