Not to completely hi jack, but, go to YouTube. Type in MOPAR Pro Stock Chrysler Australia. You can see the R4/P5 in action. They're limited to 400 c.i. If someone can post the link, go for it. I'm too stupid.
And they are using that block? I've seen some pictures of the stuff Bob Book was building for that and I don't remember him using a skirted block for that.