The only thing better than big cubic inches... are more cubic inches...!
Stump pulling torque and awsome midrange on taller gears...
However, a lot of dirt circle track guys around here are backing away from the big 434s and 421s and going back down to the 406s and 383s for more reliability and longevity... but it is hard to find less thans 377s unless the rules dictate 360s or less...