Pat, I'm in my OCD mode looking for the design of the pedal crank assembly that you are describing, like Tom the only thing that I've found recently is this below which I think you already have.
HARLEY - Google Patent Search
Here is a pic of the pedal crank as patented by W. S. Harley filed in 1912 patent granted 1914.
It may be possible to design one from scratch with your skills Pat.
Pat, ? Do you also have access to or do you plan to cast your own parts for your products ?
I do know that die casts are not cheap but once you've got em they'll pay for themselves, if those guys over at Timeless motor company can reproduce a 1910 Harley, Pat I will only guesstimate at what you can do with your skills.
Pat, here is another 1912 patent drawing of the rear triangle pedal crank looks like left side single drive with drum brake rear hub.
If there is anything I can do research or otherwise within reason, don't hesitate to ask Pat!!!
Peace Crazy Horse.