Im possibly fitting 2005 2.0 sti jdm heads onto my 2.5 fully forged bottom end, what head gaskets do i need and whats the best make?

Also how do i know what thickness to get?

thanks

 

Currently RCM or Cosworth.

 

You will have to cc the piston in the bore, & head combustion chamber & work out which gasket thickness you require to get the desired comp ratio, as a rule if you have std type piston crown & squish height they are around 22cc & those heads depending on how much they have been skimmed are around the 48.5cc.