What used shock specs?

Some have recommended buying used shocks to get high performance shocks for a good price. Unfortunately very few used shocks are listed as compatible on a Grizzly 700. On Ebay they usually don’t list the specs. say what make and model they were made for which seems . Supposedly some snow mobile shocks are a good option but finding the specs for the shocks is challenging. I can’t even find the specs for Grizzly’s.

What should I look for? I imagine the most important feature is length. Is longer than stock fine but shorter unacceptable?

Weight capacity is important but since good shocks can be rebuilt and re-valved, maybe this isn’t an issue. Probably a shock made for more weight is better than one made for less.

Is there a source of this info?

By the way, I’m considering getting adjustable shocks like Elka 4’s for a 2016 Grizzly that I plan to get this Friday (July 1, 2016)

Thanks!