I'd also like to point out, I think most know this, but I think the simpler the engine the better. I wouldn't convert my Cat 3126b, because it has a fairly complex injection system, injectors are real expensive and are already failure prone. The fuel needs to be filtered to 1 micron or the injectors WILL get clogged. I have heard older motors with mechanical injection don't have as small holes in the injector and are less sensitive to fuel not being as clean. Also, I am not sure how all the electronic sensors on it (intake air temp measuring, boost temp / pressure readings, EGTs, etc) would measure the slightly different fuel, it may throw some measurements out of whack and throw codes and cause it to run weird. Just speculating, but I would think a simpler mechanical engine would be better.
For that reason, it wouldn't be economical for me to do it, I don't think. I don't drive it more than 5k miles per year (will be about 10k this year but still) and I would have way more into the equipment to get that oil absolutely water and debris-free than I would save. If one injector gets trashed, it is $250 for a reman one plus the time and effort it takes me to replace it. $250 is almost 1000 miles worth of fuel for me.
Don't get me wrong, I love the idea of doing so and would love to build a conversion at some point. However, I would need to do it to something I would use more, like a daily driven car, and one that is simpler and less expensive to fix like an old 300d mercedes or something. Which I would have one of if it was easier to find them in a 4 or 5 on the floor!