This has been a fantastic thread and applaud you on your efforts to bring this M600 back to life. I have both a M500 and a M610 so understand both the challenges and rewards of working on the belt-driven skid steers. I apologize for joining the discussion so late but had not been able to get on this site for about a month. I am in the same boat as you were concerning my fuel supply- I suspect that my fuel pickup tube is broken or clogged because I can also run my machine with an external tank, and have also contemplated once I fixed that to go to an electric fuel pump. I would really appreciate some additional detail/photos on how and where you cut the hole in the tank/frame wall, how you addressed purging vapors during cutting, how you cleaned the tank, how you plumbed the pickup tube, and where you mounted the electric fuel pump. Also I recently started parting out my M500 for another forum member who restored his M500 so would consider pulling additional parts off as needed- the engine is a Koehler so wouldn't help you but my understanding is that the M500, M600 and early M610 have a number of interchangeable parts otherwise. Again, great thread!