400 is an obtainable number on motor. The 5.7 guys are making it a little easier on a stock rear end and stock blocks becuase of rotational mass, very little actual drivetrain difference. Their cranks are lighter. That motor is just a little better on the dyno. Not to many trucks are dyno queens, heck we have a 330hp truck on here runnin 12.4.

A good cam selection, high compression, some "massaged" heads, through a 4l60e and you will be thier. 4l80e is going to suck a little more power.

DLH2006 hit like 381 or 391 with a 224/224. You dont need a HUGE cam like the trex, actually that cam is to big for a DD IMO. The torquer 2 or something along the lines of a 230/233 in that area is capable of making 400hp. It aint all about the cam, that just helps a little bit.

Good cam selection
compression
heads
intake.

Those will net you over 400.

 

5.3 5.7 and 6.0 have the same cranks. I've never heard anything about them being lighter.