Go with the 406" i've got a 377" in 3250 lbs and it has no torque for that much weight, even on alcohol. i had a 406 on gas in the car and ran better and quicker 60' times. But i broke it because i didn't have good rod bolts in the pink rods (boke a rod bolt)
The 377' in my car is a 2 bolt, and the 406" was a 4 bolt blk. Luckly it didn't kill the 4 bolt block and i still have it
JMO
Zip.