I wish you would let me do a set of W-2's for that engine. I'd use my valve job, port work including the intake manifold and I'd pick the cam and see what it does. Me thinks I could do 650-660 pretty easy. And the torque would come back.
Here's the deal...you find the parts, I do the work for free. Including plenty of bench time.
Let me know. I'm dead serious. And I'll do it with a valve no bigger than a 2.055. May even be a bit smaller like 2.040 or something. And probably a 1.50-1.55 exhaust valve. If it didn't make 650 I'd buy all the **** back from you. Plus, I'd like to fly out to the dyno test. If possible.
Let me know. I'm ready.