Very sweet! You say they're Bill Mitchell blower motors, but you didn't say what power they are.
I visited Bill Mitchells shop many years ago, Roncomcoma, long Island NY, very cool place, you don't see a lot of his motors in the marine sector tho.
I went there with Dennis Farrara, of 'Farrara Engines', who used bill for all his supplies.
Dennis took me out in a Scarab 400, which he'd just built and installed a pair of 650's in, and promptly put it aground at 50 knts
Very embarrasing for Mr Farrara!, a quick call to 'sea tow' and we were off again.