In my humble opinion, If not out of your budget. Get rid of the ladder bars they are violent on the hit. And put in a 4-link. Second. why a 6000 stall? Seems excessive to me, you have a torque monster. I would guess 5000 to 5200 stall. And if you are launching at 4200 you are hitting your convertor harder and possibly making it stall even higher. Good luck to you I'm sure you will find your sweet spot.