Holley carb jetting advice

I have a 408 ci magnum engine very similar to yours. Mine has RHS magnum heads but probably flow close to yours, same duration cam, 10.8 cr. The diff is a Holley 870 street avenger carb. It was/is dyno tested and driven in ND. Jetting initial 82 prim/78 sec. After setting A/F ratio during dyno pulls it is at 78 prim/78 sec. It still is a little rich but I drag race it more than street time. Tuner said carb is a little big could use 770 cfm, but I don't want it to go lean. Good luck