A too-high float level isn't going to make it drip...unless it is SO far off that with the floats jammed all the way to the carb body the needle still isn't being closed.
That's unlikely.
I don't see any reference in this thread to the input needle/seat.
Howcome?
That's the FIRST place to look given: gas off, bike not leaning, still drips.
Consider...with the needle/seat working properly why would it matter if the petcock leaked or not? It wouldn't. IF the bike is leaning to the extent the overflow is 'satisfied' before the needle/seat is closed, then you'll certainly have a bike that pees.
Again.......that's not the issue here. You mention the bike is on a crate and upright.
IF the needle/seat is bad it won't matter WHAT your float level is set to. It doesn't matter!
Back to what jim said...replace the needle. When you do that, use a cotton swab with a strip of wet-n-dry paper (4-600) wrapped over the tip and burnish the seat. In most cases, the seat is NOT a replaceable part...don't know about your carb in particular.
I've used this method to resolve peeing, leaking bike carbs many times. Also, btw, to clear up fuel starvation problems related to the needle sticking in the seat due to a ridged needle and/or gummy/corroded seat.
Skip the petcock (and the idiot dealer). Call sudco or carbparts and get an inlet needle AND a seat if yours is replaceable (it is if yours is a holley! ;) )
If your needle tip happens to be brass (as opposed to viton. Doubt it is brass), dress both surfaces with wet-n-dry, and that will probably take care of the seepage problem.