Original Defender lock barrels

[100SRV]

I've seen a few Web pages showing how the "original" Defender door and filler cap lock barrels can have the tumblers swapped so one key fits all.

Is there only one set of tumblers used or is it more complicated?

TL:DR
Is it likely that I could dismantle a barrel lock on my Defender and make it match the others without requiring extra parts?

[hidetheelephants]

You can buy sets of matching key barrels, so changing them must be possible(he says having had a set on the shelf waiting for motivation to do the job for 5 years).