VHB 29s will fit onto the original V700 manifolds that had SS1s on them, the inlet of the carb/outer diameter of manifold where the carb goes on is the same diameter - 35 mm. The only functional difference between the V700 and Ambo/Eldo manifolds is the angle. One or both carbs might have to be tilted at an angle due to clearance issues (bowl against bellhousing).
If you use manifolds meant for VHB 30s, you'll need the plastic reducers to match. The outer diameter of the VHB 30 manifolds where the carb goes on is larger at 37 mm. Those plastic reducers are no longer available.
To summarize: plastic reducer dimensions:
VHB 29: 35 mm ID × 40 mm OD
VHB 30: 37 mm ID × 40 mm OD
Personally, I'd stick with Ambo/Eldo manifolds with the correct angle, inner and outer diameters.
Whatever manifolds you choose, you'll want to retain the intake port reducers/velocity inserts as shown at the top of this photo. Without these, air velocity slows and funky running is the result.
