4v underdrive pulley questions

I pulled a set of underdrive pulleys from a 93 or 94 Lincoln Mark VIII with the 4v 4.6. The set consists of a smaller crank pulley and a larger waterpump pulley. The size difference is very noticable compared to stock. However, I can't find any name brand or markings on these pulleys. They look to be nice pices of aluminum though.

So can I bolt these onto my 97 GT 2v? The crank pulley looked to have 2 keyways, for whatever reason. Does the crank pulley act as a balancer? Also, do you typically need a different length belt for underdrive pulleys?

Thanks for the reply. One more question... Are these pulleys meant to be used as piggy backs? The car I pulled them from didn't use them as a piggy backs, but the crank pulley doesn't seem to have enough weight to be a damper at all.