If they are long travel blaster front shocks they might be the same length, but in the world of suspension 1.5-2" is a huge difference which is what we're talking about between a stock blaster and a stock 700.
Assuming for a moment the length is identical, the spring rates and valving were not setup for the additional weight of the 700 nor is the geometry the same between them. There's also no guarantee that two shocks with the same length necessarily have the same length of travel. If you're going to do some flat track riding, drag racing, or putt around at 15 miles an hour on a trail then you might not have any problems. But the whole point of the aftermarket suspension is to be able to push the atv further, faster and harder than before and/or to be more comfortable in the process. Unfortunately this swap is unlikely to provide that for you.
Edit: I was focusing on the fronts but whether it's front or rear the same concerns apply. If anything, the rear is a bigger issue because the spring rate and valving is even more critical due to having all that force on one shock and different linkage setups on the two atvs creating different geometries and progression.