Harley motor in a homebuilt?

"David Hill" wrote
I'm working on a replica of a 1924 airplane originally powered by an
Indian Chief motorcycle engine. I've spent a year or two trying to find
a modern engine that somewhat resembles the Indian, and the best I have
come up with is a Harley-Davidson.

Do you really want your airplane to go "potato-potato-potato..." ? :-)

And on a more serious note, isn't the 45 degree configuration a lousy design
for vibration (or an excellent one, depending on how you look at it ) ?

Eric