www.454ss.com Should have some info. Its a mark IV. The compression ratio is I think a low 7:1. like 7.2:1. I have a 454ss and the heads suck. The bottom end is great for boost because of the low compression ratio. I am not sure if this is true but, on other forums I have heard of guys making 600-800 rwhp on the stock bottom end with twin turbos running 20+ lbs of boost. Of course I dont think those guys are worried about longevity. I know alot of us ss guys are running superchargers and running 12's and 13's on around 7lbs of boost. My 454ss makes great power and just has a set of headers. The motor is all about torque.
Yah I love my 454ss. Its very impressive for a 19 year old truck. Mine was a little beat up and mal-nurished but it still is a beast. The first day I got it I blew the doors off a 1996 z28 and a 1968 mustang. It will chirp the tires from 2nd to 3rd. The torque is awesome.