Back in the 1988/89 time frame when I tinkered with the Fox Q-500 428 engine, no doubt I got the planes up to the 150mph range in level flight.

That is..... those times I got the engine to stage on the muffler and stay there without getting hot.

Not sure what a current Fox .46 ABC can do..... but who knows.

We do know, that a well prepared Shrike with a SJ-50 on it will make it up around 150 mph. So perhaps, a point of reference.