While the head is off check how your valves are sealing. An easy way to do it is to stand it on its side so the ports are facing up and fill the ports with gasoline and watch to see how fast it runs past the closed valves. It is a good way to check to see if any valves are slightly bent or in need of a fresh valve job.
exactly what he said...i just got done with a 95 ls doing almost the exact same thing...ended up couple of the intake valves were bent..and while i was at it new stem seals and valve job....and a rering wouldnt be a bad idea also.....hows the piston to wall clearance? any excessive piston movement...g/l with this..
mike