[Lynn]

For 1969, 298 is correct for a Z/28 with flat hood.

270 is correct for Z/28 with ducted hood (or any other small block ducted hood car).

Am I backward on that?

Pretty darn sure the only difference is the bracket. I always thought the 298 had the standard bracket (more upright), and the 270 had the lower profile bracket (angled back farther) to clear the ducted hood air cleaner.

If you don't have the correct bracket for a ducted hood car, it is easy enough to simply bolt on the one you have, and use an old coil to bend it back towards the firewall so it clears. Not perfect, but works in a pinch.