I'd be keeping the webers and looking at my inlet feeds...all the way from the tank to the carbs.
One of the problems with a resto like yours is...how clean is the inside of the tank after all these years....whats the inside of the lines like...did ya run a few litres of fuel from the lines to flush them properly before you hooked them up?
Did you install some good free flowing but fine filters.
If the fuel is yukky..then it dont matter whats sittin on top of the motor, you will always have problems
you all take care