head gasket?

hi,went to buy a head gasket for my 200tdi and was told that there is 3 kinds depending on thickness?,as i'm going to put a ported head on what 1 should i get or how do i know,i'm going for a whole topend rebuild but i'm using the pushrods and rockers from my original engine.
any help would be welcome.
thanks

look at your current gasket, there's a tab that sticks out the side of your CH with holes punched in it which tell you the thickness. If no holes then replace with a no hole (thickest) gasket.