Adjusting floats on a Carter 2bbl

"Usually" when you buy a "carb kit" they will show you the specs (measurement) and how to set the float level

Also, this info should be in your service manual. You can download a '66 manual, which I'd bet is same or close, here:

(You'll have to "diddle" the page no's, the "reader" page nu.s don't follow original Mopar page numbers)

Scroll down the thread and look for the '66

http://www.forabodiesonly.com/mopar/showthread.php?t=132309&highlight=manual,+download