Ok, I'm in the UK and did it the hard way. I sent my 4300D from my '73 Q Code back to the guy who advertises on eBay as being the ex-Pony carbs expert Kurt of KP Carbs AKA 'Carbontooters1' and has many thousands of 100% feedback. The money side of the deal was reasonable,.. the shipping (to and from the UK was expensive).
The Carb came back looking quite pretty apart from the 12 or so? main body screws which had been changed for bright Chrome and looked very out of place.
When I enquired the rebuilder Carbontooters1 comment was, it was a great condition carb to start with and no issues with the build!
However, I re-fitted it and started my car. It fired instantly then pissed out fuel everywhere, lots & lots!...lucky not to have a fire...No Way was this bench tested before being returned to me...
Long story, cut short. I had my car trailered to a well respected American Car specialist here in the UK and he found....
...A twisted new main body gasket actually protruding into the venturis (I have photos to prove) and wrong size Float (yes, the one that was in the carb when carbontooters1 received it but it had not been not found by Carbontooters1 even though I'd phoned him and he'd assured me he would 'check it all out') ....Once the Float was changed out, other issues sorted and another new main body Gasket fitted and the carb correctly adjusted it has run like a dream, starts within half a turn of the key and runs/ticks over and revs out perfectly!
Carbontooters1, the USA rebuilder suggested I send it back to them for remedial work (From the UK)...Yeah, right! Anyway, eventually quite a lot of money spent but am now happy! Carbontooters1 seems to have a good eBay/online reputation but his mechanical work left a lot to be desired...All they basically did was clean the Carb and make it look externally pretty!
I'm now happy with my original 4300D FoMoCo Carb but it seems to be a slightly tricky beast that not many are prepared to deal with or know how to?