the head surface milled to a 8 - 12 RA. The block needs to be atleast that smooth or smoother. The OEM gasket is more forgiving - it allows for 20 - 30 RA on the heads.
BTW if your machine shop doesn't know what RA is or dosn't measure RA - you better find one that does.
Harry
Formerly yellowzxtt
" If it doesn't make it faster, i don't care " Please visit www.ztuner.com to GO FASTER