Thanks for the input so far Ron and CNC-Dude. Like CNC said, my thinking is that since I've gone this far I should probably get the deck milled. Out of curiosity, what kind of gap would absolutely require the deck to be milled?

Oh and he didn't mess with the head. I'm planning to take the 848 head from the 235 in my car now and drop it onto the 261. I'll check out how flat it is when I do the swap.