Rebuilt carb can't idle - 68 Cuda

If the float is too low / high (depending on your perspective) the needle will not allow fuel into the carb fuel bowl until the fuel in the bowl is too low. In a nut shell there are passages in the carb that siphon fuel from the fuel bowl at idle. if the fuel is below that port level no fuel will get into the engine. at a higher RPM different ports are in play and they might be in fuel the entire time.

Keep plugging at it.

only other idea at this time is a plugged passage after carb cleaning. the fine sludge could have gotten into some of the small ports. if all else fails pull it apart and blow air through every port and hole you can find.

Oh one other thing many kits have multiple gaskets perhaps you used the wrong one and blocked a passage, or put in on upside down and blocked a passage. I have a few dozen photos of my 2bbl carb rebuild including tear down if you want I can e-mail them to you. PM me if you want.