I have a Mark IV and I just bought a Mark VI for a good price. Can you tell me the differences between the two? Will my Mk IV oval ports fit on the Mk VI? Will my offset stroker crank in my Mk 4 goe into my Mk 6?

Mark IV heads will work on a Gen VI block but not on a Gen V,the VI has the coolant holes modified to be compatible.The VI has a one piece rear seal,where as the markIV isa two piece seal.There are rear seal adaptors avaliable.The Gen VI will have a composite 6 bolt front cover. John