Jerry - the Holleys are from a 302, not a 270. We occasionally sell a kit for one, but have never sold a complete unit. Not popular outside of the military crowd.

The BB-1 is most likely a 517s from about 1941; which is the most common of the Chevrolet BB-1's. The 517 uses the castings pictured. I have several, and no need for more, but thank you for the offer.

Jon

Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
If you truly believe "one size fits all," try walking a mile in your spouse's shoes!
The Carburetor Shop