Hmmm, I'm getting ready to swap in a rebuilt magneto from Bill Watson this weekend on my 274A5. I'll try to take some photos although I don't think that I'll try to compete in the stream shooting competition...
I've also got to mount the new tires...
Update:
I had to call Bill while working on my Mule... He has a page on his website that details how to ensure that your magneto is properly timed. Only thing is that the illustrative photos and directions are for a Mule that has the "stock" pully on the crankshaft. Mine was rebuilt at Ft. Campbell in 1981 and was converted to electric start (and wide tires/fenders) and got a double pully installed that does not have the timing mark on it. Bill said that the trick was to pull the nut and washer off the crankshaft so that one could see the keyway on the pully. When it is straight up (at the twelve o'clock position), the engine is in the right position for the Magneto to be clicking. Thus, in the attached photo, I have marked the small diameter pully flange in line with the keyway, the larger diameter is marked with an arrow to show when the magneto should be clicking (inbetween the 28 and 18 marks). I also marked the 28, 18, TDC, and -5 marks on the fan belt shroud.
Hope this helps someone down the road...