Yes, Red Power is a good source of information and I posted a message several days ago on the forum there asking if anyone knew the size of the nut. I live in the State of Washington.County Line Equipment near Tacoma, has a TD 6 engine. I'll drive there and measure the crank nut on their engine. The other thing is that I've thought about measuring the nut several times during the last 40 years. Last time I took it off , probably 40 years ago, with a punch and cold chisel. Other thing is that I have a spare engine for the TD 6 sitting on my shop floor. It would have been very easy to measure it when I was there the last time.