Any ideas how to mount a sprocket on a WorkMan Shaft?

Hi All, I am new to this form. I have an 80 cc engine that I have on an old mountain bike and it works great. I recently purchased an old Workman Trike. I'd like to mount motor on the bike but mounting the sprocket on the shaft is proving more difficult and I am unsure of how to go about doing so. I've looked at Mcmaster.com for some ideas but I thought I'd throw it out there to the community, I'm sure someone out there has some good ideas! Much to my surprise, it seems there is a differential in the shaft, also, the bike is a 3 speed. I may have to weld a bracket on the unit for the motor. Pictures below. Any ideas would be greatly appreciated! Thanks!

A fellow at this link mounted a Staton-Inc kit to his trike. You may get some ideas from his page.
If you haven't done so already. look through our dedicated trike sub-forum on this site too.
http://hstrial-rchambers.homestead.com/MB-trike.html

Thanks for that info! I will also try the sub forum!