Carb help!

IMO, 10 isn't close. Double it for a mid 230's cam in a 340. Will need 18-22ish.

I know 340-8bbl has a cam/compression in similar range and he's running more than 20 initial.

Give dist a twist CCW and see if the idle comes around. If the engine picks up RPM when you twist CCW, it wants the timing at idle. Going to have to shorten up your mechanical to get total number right.