Not personal, but the idea of a "universal" L6 carburetor is appealing. The practical application is less so.
Common L6 engines range in size from 144" (Falcon) to 308" (Hudson) with hp between 85 and 165. The same venturi size, air bleed, etc. simply won't work on all engines, regardless of adjustments. There is also no mention of what throttle disc and venturi size are furnished, and no mention of how the power system operates (power valve? metering rod?).
I would focus on carburetors known to be suitable to your engine even if not OEM.