Has anyone O ringed their head or block on the l6?

And does anyone use or have heard of people claiming to use mains caps greater than the standard 2 bolt mains?

yes and no

How much power do you think you are going to make?
How much money do you have to spend?

the best you are going to get main caps wise is the facotry main girdle that is already fitted to your AU,
That AU main caps are already cross bolted the cast alloy sump and leaves not room for the 'traditional' 4 bolt setup.

We've all tolorated you attitude for long enough mate. We've pointed you in the direction of the info you want, go and read the 6cyl guide sticky at the top o fhte forum. then go and start reading through the forced induction section.

There are really only two outcomes, One is you have the $20 000 - $30 000 it going to take to have this 30psi 1000hp angine built, in which case asking questions on a forum is waist of everyones time.

OR

you have enough money to make about 300rwkw, in which case you put 14psi into the stock un opened AU engine that you have get a good tune and enjoy having more power that the car can put the ground.

If you go and read all the sticky posts and all the stuff in the forced induction section and you still have questions by all means ask away, at least they will be informed and sensible questions.