first of all the tuned version of an engine:

• all parts are checked so there is the best fit between the parts(piston cylinder). they are choosen by hand
  
• also when it says tuned it means that the crankshaft has been worked, and is now lighter since it is worked some metal is gone... and also the crankshaft "hole" is widened i think and there is also a better fuel flow since it is polished.

so in the end the tuned version is always better(meaning faster) than the "stock" version, but cant say that the stock version is not fast, its Very fast also.

NiTrO BoOsTeR to answer your question, i always have the same problem what i do is check the underside of my head, because there are marks left from the button head. i think it doesnt really matter which site the button head is...
hope this helps