The air restriction is one thing I was worried about, as was the propensity for the 4.3 TB to be basically shooting right against the walls of the taper from 2 barrels to 1.
Probably wouldn't be a problem. The 4.3 TBI has the injectors above the throttle blades which means the injectors are spraying against a mostly closed throttle blade 99% of the time. This actually causes better fuel atomization than the newer TBI's with the injectors below the throttle blades because the fuel sorta puddles up on the blade opening and the air has to pick up the fuel as it goes by. As long as the adapter is tapered I doubt it'd be any more of a problem than the abrupt 90º turn the air/fuel makes going from a carb/TBI to the runners.
