Those old evinrudes are pretty cool. I picked up a rough but running 72 Norseman with the opposed twin when i was broke and had no sled in university back east and had a ton of fun with it. Ended up picking up a 2nd motor than had CDI ignition and a better carb and the true dual pipe/muffler set up and swapped all that in, cleaned up the clutches and replaced some bogey wheel bearings and that sled went pretty good. Track was made of 3 pieces of conveyer belt with metal bar cleats. Didn't have a trailer at the time so I would load it backwards in my suburban...
I used to trail ride it to the wing nights at the snowmobile club
Everyone thought I was nuts (rightfully so).... the brake cable was broke so you had to stop by sticking your feet out which made for some interesting situations
Unfortunately it met its demise with an electrical box in a ditch...
I always located parts through guys in the snowmobile club, but there is alot more vintage enthusiasts back east in Ontario. Ebay used to be good but I think its kinda fallen off now...
Post some pics