I have a contribution to this thread!
Picked up this SketchyTrike™ over the weekend for $40...
The middle section of the frame actually looks like it was from a commercially available product, but the rest is definitely homemade. It has a Tecumseh H50, snowmobile torque converter clutches, jack shaft, and live axle. Somebody put a ton of time and effort into assembling this thing. It had been sitting out in the rain and there was water in the oil, gas tank, and carb.
It took about an hour but my dad and I got the H50 cleaned up and running (carb was full of rust and had a bad main jet seat) and got the throttle cable freed up. It has a top speed of about 20 MPH and is super sketchy. It's hilarious and the running H50 is probably worth the $40 alone. It still won't idle but I suspect the carb just needs rebuilt.
And of course a pic sitting along side my Tricub.