They way your system look I would go through all 3 carbs , it seems someone patched it together to make it work , I would swap the power valve , but measure the vacuum first , you need to have 2" more vacuum than the power valve rating idling in gear if auto so if you have say 10" of vacuum put in a new 6.5 PV , but if you have 6" go to a 3.5 PV
61 was the stock jet so you are good with 62
Could be bad gaskets , PV , Fuel level , or other internal leaks causing the flooding or loading