These twin carbs are mechanically linked together so they come pre-sychronsized. Balance tube included. Pre-jetted. Special custom length manifolds give plenty of frame clearance.
In my Featherbed for testing.
Options include airfilter and plumbing kit below

Plug color with tuned Keihin carbs
Curved manifolds with balance tubes for tilted engines
Alternative straight manifolds with balance tubes for vertical engines
Thin ham can that will also fit the FCR33 from RGM