Bigfoot primary compatible whit Vanguard Secondary ?

[benzine]

Hi guys. Who know Bigfoot primary clutch 127-73 compatible with Vanguard secondary clutch? My old engine was B&S I/C 16hp. New engine is Robin Subaru 20.5 hp. Crankshaft fore primary clutch on Subaru is key way, on Briggs, threated. If I have Bigfoot primary clutch? may be these idea required secondary Bigfoot clutch to?