Anybody know anybody who has an MRL perf 318

Do they only do complete rebuilds crate style, or can Mike prescribe a recipe where I can use some of my current stuff.

Yes...to all.

Seriously, if you haven't looked up his vendor page yet, and it appears either you haven't at all or not much, go through all his posts. I ran through there a couple weeks or so ago and noticed he did at one time have a DD 318 type build. I get the impression no one gave those much attention so he has other builds available, and has built other engines for customers here on the site...much like the 340 you mentioned.