Cosmo - it is important to MATCH three identical YH carbs. Mismatching will cause major issues.
The Dearborn Marine 2617s and 2618s are probably the most common, and these two numbers ONLY can be mixed.
As to the Corvair, there are seven different. Of these, the most common is the 4141s (also the most expensive) as it was the last, and sold as service replacement for most of the others.
Jon.
