Here is a link to a thread on the HAMB about a '29 Chevy build using a 216 with a RAJO head. I didn't know there was such a thing. There is a Rajo brochure that gives a lot of info. Very interesting head.

LINK

Thanks, didn't know about the single Zenith.

When I saw the pictures of the one with the stock intake it made me think that I had seen one when I was a kid. I always enjoy seeing what those guys did back then without computers. I wonder why he chose a Zenith for the secondary?

Just a guess: the Zenith covers all starting, idle and part throttle cruising with the smallest venturi for best response and mileage.
The 3 X 1 in the original ports provides WOT power without the concern of bad distribution due to progressive linkage.

Years ago an XO LSR team tried to modify a Buick L8 using the same technique (extra port supplying the siamese bowl and valve) and were given permission. When the car turned out to be fast, they said it's illegal. Very disappointing.