[Seattle Sam]

Scott,
Are you rebuilding the carb yourself? I highly reeccomend "Rochester Carburetors - Tune, Rebuild or Modify" by Doug Roe. The book will explain all this stuff in gory detail.

You can change out the primary jets to richen or lean out part throttle (slow to half throttle), .068 to .077 sizes are available from Edelbrock. You have to have the air horn and top off the carb to change the primaries.

You can also change secondary metering rods (jets are fixed), which have different size tips and tapers. This affects part throttle to WOT. If you don't drop the screw or rods down the carb throat, you can change them easily with the carb assembled and installed. Edelbrock has five sizes of metering rod available from .0300 to .0667, the slimmer the rod, the richer the mixture.

Finally you can change out the hangar for the secondary rods for earlier or later lifting of the rods out of the secondary jets. This delays or advances when the full fuel load hits on WOT by lifting the metering rods at different times relative to when the secondary throttle blade opens.
Don't know where you can find hangars, except at the boneyard by stripping old Q-jets. That would be a good source for rods too.

Good luck!
-Sam