I was impressed with the build. Looks like you ended up with 1.86hp to cubic inch after the contest. I was very impressed with all the things that were done within the letter of the rules.
I had the opportunity to meet the Mummert's at Bakersfield a few years back. They were running a 292 y-block in a '64 Falcon sedan, making 10.40 second passes. Using their heads, a spider type four barrel intake and I guess their own headers. So I do believe you are right on them just not doing the Y-Block build in the magazine right.
1957 Fairlane 500
1965 Custom Sedan
1965 Galaxie Convertable