In starting the renovation to our 1981 22' Euro I decided to replace the old cracked stock exhaust manifolds with long tube headers. Of course all the manifold bolts were rusted so badly the bolt heads had shrunk and even an easy-out would not remove them. So I ground off the heads and removed the manifolds. That job required removing the old dead AC compressor, Power Steering pump, and mounting brackets. I will repalce the old R-12 system with the R-134A and rebuild the leaking power steering. With that out of the way and the engine showing 54,000 miles,(the last 10 years sitting) I decided to do a valve job as I suspected the heads did not have hardened valve seats. Sure enough they did not - this is a 1980 engine. We found one head had a crack from the exhaust valve seat to the water jacket though it had not leaked and that was a function of the high heat and soft valve seats. If you are restoring an older coach with the 350 GM truck engine, and maybe the 454 as well, you might want to have the valve seats and valves done. It did run OK and I probably would not have done the job if the manifolds were not cracked. Other than labor my local machine shop charged $750 for both heads (he had an older core we could use as a replacement) with new sodium filled valves and hardened seats for the ethanol laced fuels. You should expect all the older engines pre-1985 to have the same issues.