[cobrashoch]

Dan - I wrenched a set for a local guy. Matter of fact it was for a Pantera too. Engine lost about 800 RPM's on the big end and the power band was totally straight from idle to about 6200 rpm's.
Cam was a .65 lift roller with about 11 to 1 slugs and 392 cubes.
Putting back a worked over set of 4 barrel heads the engine came alive and and gained over 150 horses I'd bet, and that's with a one point in compression loss. It also ran very slightly better yet with a set of slightly worked over Aussie heads, over the four barrel heads. He's looking at a set of the new Blue Thunder heads now. Time will tell.
I've said it before and will repeat it again. Unless you have a overhead cam setup, a four valve setup will scrub off too much power to make it worth your while for performance. There are however a few advantages 4 valve heads have on low to medium performance apps. on some supercharged under "boost" conditions, and those heads above seemed to take "crappy" gas a bit better too. Overall from a hot rod viewpoint your WAY ahead to stay with a 2 valve ohv setup I'd say.
Those heads sure did look neat on that Pantera though,,,,,,,,,,,,
cobrashock