RV Repair: Cylinder Heads, cast iron engine, aluminum heads

Question
I have a 1992 Chevy 454ci P30 chassis. One cylinder head was replaced. I was informed later by another shop that cylinder head was replace with a cast iron head and it should have been aluminum like other side. Will this cause any problems or performance lose? Also after first shop changed head (cast iron) engine made a very loud noise that was constant until engine was shut off. They told me it was a stuck valve. Does a stuck valve make a loud banging noise? Or does it sound more like a exhaust leak?

Answer
Aluminum heads were used on Corvette 454's and don't belong on a heavy duty motorhome.  What can I say, you need a cast iron pair of heads on a cast iron block.  I honestly don't know what problems it will cause but if the original mechanic is still in business, I would get my money back so I could have someone fix it right this time.  Continuing to drive the coach will only cause more damage if a valve is stuck, you are probably hearing the piston hitting the valve and that is bad, real bad.