avoid the plastic JC like the plague if you are tying a display fly! for fishing, i wouldnt worry to much about using either.
As for the looks of a Gray Ghost, this is one of the first streamers i tied (this fly isnt very good). The long topping underwing has fallen down in this photo, but i should rest right on top of the body and extend beyond the tail.
This grizzly gray ghost variant (originated by Graywolf) is exactly as the a gray ghost should look except it has grizzly hackle wings instead of dun.
One other caveat here, and you'll be hard pushed to find it in any book or online reference bar two or three - there is actually a white hackle throat on the gray ghost which has been left off virtually all gray ghost pattern listings in print to day.
For more information on this you can check Don Bastian's blog
. if mods remove the active link, you can do a google search for it.
Note that neither of the flies i tied have this white hackle throat, and the gray wolf grizzly gray ghost did not have it visible in the photo i reproduced the fly from. Hope this helps you.
In terms of you tying the fly, i'd get a copy of Hilyard's Book 'Carrie Stevens: Maker of Rangeley Favorite Trout and Salmon Flies" for an accurate (except the white hackle throat) pattern description.