Thanks. I seem to remember that in the end Triumph wanted to use a common head for both 2 and 2.5L engines so the deeper (4.4"?) version became the common one fitted with flat top pistons on the bigger engine and domes the smaller to get the correct compression ratio. The MK3 GT6 with stamped head number 219015 is an example of this so should, according to the list, measure 4.4" and have domed pistons. Obviously if flatties were used with this head in a 2L the ratio would be lowered....