Your vortec heads are from GM and for 3/4 and 1 ton truck. You have a single ground valve with the harden set installed. GM did this to keep the exhaust valve cooler under heavy load, and pulling that load for a long time. Vortec heads like to crack on the exhaust valve down the runner with out over heating. It was a big issue for GM, and they came up with the install seat to fix the problem.
If you are going to use the vortec heads for a truck to pull heavy loads. Keep the seats, and use the single ground valves. You wont crack the heads, and will get a long life out of them.
If any one can help.
I am trying to find info on the 906's to tell if it came with small ports, or large ports. I have a set of 906 vortec with three angle ground valves. Witch should be the sawtooth heads. But this set of heads don't have the sawtooth on the ends. Nor do it have the bowtie, and GM castings. If any one can lead me to more info, or tell me more about these heads.
I thank you.