I am doing the same Ghost( Alot of people are doing this now,right Vicory
As Hi.Spec said, JG and AnK require the HurricanE adaptor set, you can find it on WGC.
The D-boys, can be assembled right onto the Guarder body, but you will need a Barrel nut and a new outer barrel. The outer barrel is no problem if you are getting the VFC M468 barrel. I cannot seem to find a barrel nut all by itself. I can only seem to find them in sets. And the cheapest set is.......The HurricanE adaptor kit.
So, if you have a old Armalite lying around, you can use it's barrel nut. If not, then you will have to buy the kit, unless you snag one from a friend.
So, both will cost the same. I am thinking of using the JG to do this simply because I can throw in the M468 barrel, and call it a Barret upper on a Colt lower until I get the Metal body.
However, The D-boys has the millitary Sir, the one used in the real M468.