Info needed on SB Heads

Guy last night offered me a set of "596" SB heads for REALLY cheap. Totally done with new guides, seals, springs, 3 angle valve job, yada, yada - one of those big idea jobs that got started years ago and is still at the same stage of progress as it was then. Heads aren't assembled but he says he has all the valves, springs,etc. in a box with the heads. I currently have a set of 915 "J" heads on my 360 but they'll require a fair ammount of work during this upgrade. Need to shave them .030 or .040, new guides, seals, springs, re-do the 3 angle valve job - the usual. I haven't seen these "596" heads yet and I'm not familiar with them at all. Does anyone know the original application, average chamber cc, valve size, hardened seats or not? I'd like to be armed with at least a LITTLE knowledge before I go look at these things. :)
Thanks.

Sid