Maybe an other head producer in the game.

Crazy thing is my Indy headed 422 ran 5.98 with my son driving.

My Edelbrock headed 408 ran 5.98 with my son driving. Both ran 6.00 many times with me driving.

The 422 had a solid roller lifter .650 cam and the Indy headed engine ran a .650 solid lifter cam.

My Indy 360 have room for porting improvements but my Edelbrock heads were ported by me back in 2008 and have lots of room for improvement. My 408 shocked the heck out of me when it ran 6.0’s on its first weekend out on its first pass. Don’t write off Edelbrock or Speedmaster heads.