Richard,
We've got the Aussie 5.4 motors with Quad cam heads in a lot of the Ford Falcon performance models down here. That motor is even bigger again with the taller deck height of the 5.4. I did a quick tape measure of one in an XR8 Falcon a while back and it was about 900mm across.
I was looking at one stripped on an engine stand and the heads look great but the tight bore spacing was a bit dissapointing. The 5.4 is very under square and there is no room to bore them out any further unless they turn it into a big V twin with two oval pistons.
Cheers