As GM proved many years ago, a good starting point for a non-traditional motor (where you can't just start with "what always worked before"): the Sprint OHC 230/250.
1. enough CFM to provide any power level the stock motor can produce without pumping loss (over 200 hp)
2. big vacuum secondary, adjustable in total air-flow, opening point, and secondary mixture
3. small primaries for good response and mileage
It's called a "QuadraJet"...!
Downside:
- it's got to turn sideways (from the V8 position) to put the primaries facing the intake ports on an L6 (linkage = fun)
- it won't fit the common Clifford etc. 4 bbl. manifolds without an adapter, and adapters may not provide the flow pattern you want
- because the secondaries are so big, the plenum is also big, which damps response somewhat
