Hi bowtiejoe . . .
Your '36 project sounds like fun.
Progressive linkage isn't typically used on a dual. The carb placements favor the front and the back of the engine respectively. Choosing one as primary and the other as secondary could lead to lean conditions on the other end of the engine.
Carb placement is the primary benefit of a dual over the single. The stock single setup has a tendency to run the cylinders #1&2 and #5&6 leaner then the #3&4 which are closest to the carb.
Buick used a progressive 2 deuce setup in the early 40's called 'compound carburetion'. The manifold had a split log and a baffle that blocked off the rear carb using the front carb for most driving conditions. But when the throttle position was sufficiently 'open' the baffle would open and the rear carb would join the party.
Buick Compound Carburetion 
regards,
stock49
