Ok, here is the Simmons Super Power Carburetor, with the heating element as an option. It seems that not all Simmons came with one...the one I've got having been sold here on the West Coast, didn't have the heating element, the place where it installs has a plug that is removeable, if you chose to buy the element option or maybe they sold the plug with the carb incase you wanted to uninstall the heating element.
A lot of the Holley NH parts will fit, some may need to be modified slightly, but where I wasn't sure I gave the measurements (in the hope that helps).
Anyhoo, I think I've covered all the bases here, but if there is something I've missed, let me know.