Differences between EF/EL and AU head?

[bindi]

I was discussing with a friend about my idea of putting an AU head on the EA (it's an ED engine).

I know to put on an AU gasket etc... although there is a vague memory where someone on here suggested boring some particular bit out of the head (remind me if you know who you are - I think it was to get something out quicker and improve efficiency?! : Blonde moment).

So anyway, what is the difference btwn the EF/EL head and the AU head? And what, in your opinions, is the way to go? I am not really chasing performance, but I don't want to have to keep doing the head change too regularly. I want to know that once it's done, it's done for a few years.

Note: It's dual fuel too, just letting you know in case it makes a difference