the 4220 military surplus machined to fit our cases is about $350 NOS on EBAY is only $120 but you should consider machining the OD and a new capacitor. Slick 4220I cringe at the current price of a 4316 mag and harness! It could wind up being the single most expensive component of a simple, VW-powered aircraft. It makes electronic systems like the Leburg even more attractive.
Best to buy from Scott Casler