Highest LIft cam with 68 340 with stock intake and carb

You'd be hard pressed to get a batter intake and carb for what you are doing, unless you have 1.75 headers, a loose converter and 4.10 gears.

What is the rest of the combo?
391 rear gear with the stock 4 speed 833 trani no headers just 2-1/2 TTI X pipe Exhaust with an MSD ignition.
I posted the cam specs link above