these heads aren’t gonna make 700 horse.
but with a nice roller, and compatible parts, they I am positive will support 620-630 easy enough( they actually made 657 on Bischoff dyno) that on pump swill with a 263@50 roller
You can see the pull on Rods Facebook page, along with the 6.08 pass one of his customers made. Based on weight and MPH, that pass is 630 or better horsepower wise..conservatively.