Older, standard production sleds were made to go places but not necessarily get there fast. Sleds are geared differently depending upon the engine displacement and purpose. Without knowing anything more than track width, I'd predict - if entire driveline is in top condition - it's set up for a max of 30-35 mph on flat, open terrain (e.g., frozen lake). I personally wouldn't do it based upon design and age. It's >40 yrs old - don't ask it to do more than for what it's designed. if you get it up to speed and the old track gives out, you've got a problem.