I guess over the years rodbuilding fumes affect one man differently than the other man, so maybe I wasn't clear, Andy. I'll try again.
Martin USA spools consist of 4 main parts: a central hub or arbor; an inner, frame-side plate; a click-gear press-fit to the frame side of the hub/arbor; and a handle/outer side plate press-fit to the hub. The spool latch mechanism and cover is screwed to the outer side of the arbor. All of the latch covers interchange, but the spools don't on the fixed click (63) vs. adjustable click (MG3) reels because the click gear is different. (See below: frameside spool face, hub surface, and click gear, 63 on top, MG3 on bottom.)
You can't move the click gears as these are too tightly assembled to enable a home tinkerer to swap them. But you can remove the outer side plate by prying it off. That is what is shown on the black spool above, the outerside plate removed, and the outer side of the hub with its crimps shown. You can also see the screw positions (one with a screw in it) that retain the latch plate. The latch plate doesn't retain the spool plate; only the press fit and crimping does.
So if we have one spool with an outer-side palming rim and one without, we just pry them off their respective hubs, swap them and press fit them back with a little epoxy and punch-crimping to secure them. That's what I have done: removed the palming-rim spool face from a 63SS spool and put that on an MG3 spool. The non palming rim spool face from the MG3 spool goes on the other spool.
In the picture below, you see another angle on a spool with the handle side plate pried off its hub. Upper right is a conventional MG3 spool. If I had another palming rim plate on a 63SS spool, I could pry its handle-side plate off the same way.
To the left is a 63 spool, conventional now. It is shown frame-side up, but you can just see the outer-side spool edge, not a palming rim since that spool face came from an MG3 spool.
Below that is the outcome for a couple MG3 spools. Both were conventional originally. Both now have a palming rim outer spool plate swapped from a 63 palming rim spool. I'm still in business with the 63 reels because the conventional plates went on to their spool hubs.
Hope that's clear. I had only coffee this morning and haven't cracked a can of varnish or used any contact cement.
In case anybody wonders, later on Martin manufactured the MG3SS, which came with a palming rim spool. I have one of those. What I did might seem like a lot of trouble, but palming rim spools are hard to come by, whereas the ones to swap faceplates or much easier to get.