Have always heard of that setup, I even had to pleasure of riding on one from Winchester Va to Harrisonburg, Va about 1957, have been trying to learn more about that setup, driver control of both engines etc, how did they perform etc, etc.In my business,(Generators) have came across a few twin DD setups, 6-71 a left and right about 2 inch apart, into common gear setup with two clutches, starters & governors. Recall it is tuff to determine if one is not actually running under power until you get familiar and check for exhaust smoke & heat etc..Question is? Did DD use the twin setup or actually two seperate engines ? Have to guess it was the twin setup, one driveshaft etc.. In those days DD would and could design and make most anything.Just trying to find some data on this old system before the V configuration was available. Been most interesting to this gear head.Dave M