Maybe an other head producer in the game.

I find it hard to believe those heads only flow 296cfm. They have a 2.08 valve right ???

Yes. I believe that is what those guys said they flowed.
My W5’s went 301 at Best machine, and a set just like them went 299 on Vic’s bench.
Must be a very conservative bench he has, as the other poster noted, he makes a solid 680 horse at the track with them, and the short block is far from fancy. No trick rings or vacuum pump either.
Think it’s only about 11.5 compression too. Mine is a little higher because I milled the heads a little