Check this equation:

Tunnel Ram + Stock Motor = Untunable Stone

Honestly, you're looking at a tuning nightmare. I had a friend who did this. The only way he got it to work was to disable the secondaries of both carbs, and use a progressive linkages on both primaries. The primaries on the first carb acted as primaries. The primaries on the second carb acted as the secondaries. Essentially, he turned it into a dual-quad-looking four barrel. It was still hard to run because of the huge volume in the plenum.