i agree with FoMoCo but i go just a tad farther i bouce the car or truck, small amount,and set it so it doesn't slouse out the hole,maybe ,1/4 turn, so when hitting any bumps, or hitting the brakes,they don't come, up out the vents,everybody does things a little different ,most does it like your first reply ok bill
Remove the brass sight plug from the side of the float bowl, being careful not to drop the gasket. The fuel should be right at the bottom of the hole, maybe dribbling out a little. If it's not, with your 5/8" wrench and a large flatblade, loosen the large screw on the top, turn both the screwdriver and wrench as a unit, then tighten the screw. Clockwise will lower the level, counterclockwise will raise the level. Note that if you lower it, you'll have to rev the engine to use the fuel that's already in there. When you get it right, put the sight plug and gasket back in.
if you get a carb kit it explains the setting,it might mean, when you hold the top,of carb out of the main carb body,the floats will hang that much,from the top, part of carb, like the carter and edelbrocks do ok, i'll take a look for you as i'm also a 60s racer who,worked on more than holleys lol bill
well this is from an original ford rebuild kit,  upper body held in the normal position ,raise float to the closed position,than between supplementary needle and the supplementary float tab.[do not raise needle off its seat] in its list it shows max of 1inch dry float level,hope this helps bill
Put lite pressure on the needle to hold the float in the closed position and measure from the top of the casting right at the end of the float. Gently bend the tab at the end of the float as needed to adjust.