[Arran]

I think that would depend on the total depth of the new speaker cone verses the old, if it's deeper then the old cone then it may be wise to add a ring under it as a spacer just to bring it out a bit. On most of the speakers I have taken apart the cardboard gasket material was glued on top of the edge of the cone. Take your time figuring this out, I think you will need to shim the voice coil just to make sure everything lines up when it goes together. Normally the form for the voice coil sticks above the center of the cone about 1/16 of a inch or more, in this case they also have the spider glued in place above that, so I would remove the spider and voice coil from the old cone, provided the hole in the new cone is the right size, shim between the voice coil and the pole piece with the coil sticking out the right depth, glue the voice coil to the cone. Then take the shims out, put the spider in, re-install the shims though the slots in the spider, put the center screw back in the center of the spider, then glue the spider to the cone, then after that has dried glue the cone to the frame. Don't take this literally because I may have missed something.
Regards
Arran