Holley Throttle Plate
6231 is supposed to be off a 72 413 from a motorhome. Should be a 4160 model carb.
A baseplate from an 1850 holley should work on it, sans some of the extras.
I bet Fishy was thinking of a 6213 carb which is a spreadbore carb. Dyslexics UNTIE... uniet, uneit, UNITE! :-D