I'm trying to get the best of both worlds, and it may not be feasible... but I'm betting this community will be able to help make that determination.
If there were an easy way to do this, I believe it would be immensely popular, which is why I'm guessing there isn't an easy way to do this 
I've got an MTH Z-6 with a Great Northern paint scheme. I'd like to run this as a Northern Pacific locomotive with the same number (4000, obviously not prototypical for NP), by covering the "G.N." marking on the locomotive's dome, and covering the Great Northern logo on the tender with the Northern Pacific serif lettering. But... then I want to remove those changes and also run the locomotive as a Great Northern.
Some givens:
-I have an MTH 20-3272-1 (GN) and would sometimes like it to look like an MTH 20-3273-1 (NP)
-I don't need to change the road number, the text beneath the road number, or the striping
-I don't want to damage the existing GN logo/markings
-I acknowledge that the best way to resolve this would be to acquire an NP Z-6 in addition to the GN... pocketbook says to research other possibilities
-I've experimented with magnets, but was unsuccessful thus far, and am concerned about a magnet damaging/affecting electronic components in the tender near the shell. The idea was to make a magnet of the appropriate size with the desired lettering and enough black area to mask the existing logo, and place some strong magnets inside the tender shell to hold my temporary logo in place. Initial tests were unsuccessful for a variety of reasons.
-I've acquired some temporary black tape that "isn't supposed to leave any residue" if removed within a certain amount of time... I haven't tried it yet. The idea would be to simply cover the G.N. text on the dome, and then tape material (magnet, photo paper, etc) with the desired logo over the GN herald on the tender.
-I searched for other topics on this forum that deal with this, but didn't find anything, so if you can point me to an existing topic I'd appreciate that too. I probably just wasn't searching for the right terms.
I'd also like to acquire a removable coal load that can be placed on the tender to turn it from an oil burner to a coal burner. I believe a 3rd Rail version of this locomotive comes with that removable feature, and obviously I'd need to fabricate one for the MTH model - but I could use some suggestions on how/where to start.
Thanks!
