I'd like to be able to help you more, but I'm not a carburetor guru, or a Dell'Orto guru. That's why I made the comment about you will have to do your homework.
I like cool old stuff myself. That's how I ended up becoming involved with a Dell'Orto carb. There is information to be had on using these carbs on motorcycle engines, but I have not been able to find a thing in printed form on using one on a Flat-Head. Brandt at Rupp Parts is the only source of information that I'm aware of, on using these carbs on a Tecumseh. He is very difficult to contact. Make sure you have a well thought out list of questions prepared before you try to call him. It sounds like he is a one man show. He answers the phone & helps callers one by one as they come in. He might spend 15 to 20 minutes with you on the phone, while ignoring his call waiting. It may take several attempts to reach him & you may only get the one shot, so be ready.
Your carb looks like it is missing the choke & lever. I believe that is a part that is still available. Fabricating an intake manifold shouldn't be too difficult. You will need to make a flange that bolts to the head. You can use a gasket to trace out the part. Just make it slightly larger around the outside. You will need to locate some tubing that has an O.D. that will be a snug fit into the carb. Make sure that the I.D. matches the port on the head & the carb. Once you have those two parts, mock it up to insure the fit you want & tack weld the tubing to the flange. Then final weld it. If you can't weld, you can still mock it up & make some alignment marks. Then take it to your local welder.
Below are several links that I have found after many searches. None will answer your questions directly. You will have to go through it & piece it together.
Or find a Tillotson with a throttle bore that matches your intake port & bolt it on. Twist the 2 needles on the side & go riding. :evil_laughter:
Gregory Bender - Dell’Orto carburetors
ducatimeccanica.com - for classic Ducati motorcycle enthusiasts
Carburettor Settings - Ducati Vintage
Dellorto and weber carburettors online
Lambretta Carburettor & Jetting
CARB - CARB SPARES - FITTINGS -
Carburettor recommendations
Bevel Heaven Dellorto Carb Restoration services
Bevel Heaven - Vintage Ducati Bevel Drive Motorcycle Extravaganza.