Well, look what we have here!

About the best working W5 heads i know of were the ones on my 422 motor.
I sold the car, and the guy who bought it upgraded the motor from what it was when i had it. Bigger more agressive roller. Gas ported the pistons, and bumped the compression up to 14 to 1.
Motor made 708 on the dyno at Best machine, an extremely reputable shop.
Car then went a best of 9.62@ 140 at 3220 pounds on super stock springs and a 28 by 10 DOT tire. That track result backs up the dyno numbers
Thats about as stout as i have heard of. Those heads were probably 320-330 max flow.
In fact they became leakers because of porosity and max effort porting. The owner then bought another set of W5 heads and had them CNC ported at Modern cylinder head. Who has a nice program. Back on the dyno, right around 690 ponies. Car hasnt approached 140 since. I will get some more info as owner is bringing it to Norwalk for Monster Mopar event.