Andy, I got the 6.5 back together and running again. I finally got all the leaks tracked down and it has it's first oil change under it's belt. I ended up using a 6.2 block, 6.5 heads, HY-35 Holset turbo, my homemade intercooler, but decided to go with the 6.2 injection pump. I figured that the 6.2 pump would be the limiting factor in power and I was right. As it sets right now it runs about like a stock 6.5 or maybe a little faster. I did this so it doesn't blow up again so soon. I put it up for sale so I can pay for the Dmax, but haven't had much luck...
Good luck on the dually! I hope to see your twined 6.5 in the future, if you can find enough fuel and a strong block it should haul ass.
Justin