If you have an automatic transmission w/a torque converter, the stall speed will see to it that you won't be fully loaded when you floor it from 1000 rpm.
Remember its boost that you're concerned with. Boost will build quickly when the engine is loaded- but not instantaneously. While boost is non existent or still very low, the timing can be higher. You want this so the engine can spool up using the right amount of ignition lead until boost sets in, then the timing is taken away as boost increases.
It's better IMO to have a tunable secondary block
than using a 4160 secondary plate drilled to accept jets. The link is just one such example.
4150 style carbs can be mounted sideways to clear the rear bowls. Takes a different mount and linkage obviously. Enderle linkage shown on member Blown Camaro's photo below: