That carburetor has downleg boosters in it, not annular.

Can I play, can I play. Actually I can't help but I do feel your pain. I went throught the same thing this spring when I decided to rebuild my Holley. It turns out I have a 4160 with the chock horm milled off and a secondary metering block added. I even called Holley but without the numbers that where on the choke horn they couldn't even help. A guy on another site was able to ID it without even seeing a pictures. Thank god for sited like this.

I wan't to play too. Tried the substack on my 850 dbl pump with choke horn/no choke saw minimal gain 3hp. Next time on dyno tried 850 proform carb main body with everything else the same went from 563hp to 581. Now that's a bargain.

Mark

Thanks for clearing that up. I sat here and thought about it for awhile but is has been many years since I messed with carburetors.

Roby