You dyno and horsepower guys kill me. Lol. Get the damn thing to the race track and put in some work. My little 422 with a solid lifter cam has gone a best of 5.98 and a boat-load of low 6.00’s. Not at some coastal super track either. Off the shelf pistons, no vacuum pump, no special ring packs, and a bracket sized tire 4 inches bigger than needed. Sure it’s 2880 pounds but yours could be too.