My w5 heads " supposedly" flowed 330ish as well, and on one bench they went 297 and on another bench a near identical set of heads were just a touch over 300 max, so numbers are just numbers.

Mine that went 297/303/330 depending on what one wants to believe did go 9.80's at 3350 pounds on a near stock suspension, so..who knows..

But a w5 is for a fact a " small" head for a 400+ inch race motor with a huge 4 inch stroke crank...mine wheezed at the top end,at 7000+ rpm, just small head relatively speaking. That small 2.08 max intake valve just isnt suited for optimal performance on a big inch long arm motor..will it run good, sure, are the heads a governor to a degree on a big inch motor..absolutely.