I bought this to replace the failing tach in my 78, but the seller sent one from a 240 instead.
I can't use it and I've already settled up with the seller, so it's for sale if anyone needs it. I cannot guarantee it works because I have no way to test it, unfortunately. I bought it as a working unit and assume it's fine. I'll trade it straight out for a working 280 tach or sell it for $50 plus shipping.