Literature
I never had that problem with bogging. I was also running 600 Vac secondary Holleys. My Roadrunner ran 4.10s and the dually had 4.56s. The amazing thing was that I was running Crower cams with an advertised 300' duration also. I don't have the specs on them anymore but I know that they weren't supposed to develop much torque below 2000 rpm. I know my Roadrunner never launched very hard, but it didn't bog.Tried one of these on a '72 318 Swinger in '73 with a 600CFM Holley with vacuum secondaries. At a full throttle stomp from idle, it had a massive bog when the secondaries opened that I couldn't tune completely out. If you rolled into the throttle and let things progress at a more sedate pace, no problems, but that wasn't as much fun. Replaced it with a single plane Torker that wound up on 3 more cars...
Frank-n-Head
The Offenauser 360* 'Equa-Flow' Intake was the standard 'Dual-Plane'
High Rise.
The 360* 'Dual-Port' was the gimmick Intake.
Yes, two different Intake Manifolds.