It was ground up restored for the 2011 Waconia vintage show build-off when Rupp was the featured brand for that year (an Alouette Super Brute won). Found it on vintagesleds.com. Was looking for a '76 Nitro, my very first sled. This was similar but better and rarer. Rupp didn't save production numbers but it is believed 500 Magnums were built in '76 (250/340/440) for homologation and far less than 100 were 250s. It only has break in time on the stand. Some day I might put it on snow and dial in the clutches. Then back to it's perch. It's best as a wallhanger IMO.
Ah the Nitro, I stumbled on one when I was about 26 (about 1994) and I enjoyed it locally around Green Bay as we actually still received snow and trails were not developed into homes yet.
I remember it kept snapping the torsion style suspension springs underneath, well Green Bay still had a Blacksmith shop on Broadway which was owned by an old-timer. I took him my old broken springs and He hammered me out new ones; cheap too something like $12 a piece.
Bear