[Arran]

Ron;
  There is a fellow on Y.T that goes by the handle of shango066, I think his real name is Dan Yahro or something. In any event he has posted several videos on how to replace the mica caps inside those slug tuned mini cans, including finding the values. Basically you have to remove or permanently disconnect the mica cap, and then you need to connect a trimmer cap across each coil,  and then peak the trimmer with an RF generator. The FM IF cans use small values, in the tens of MMF/Pf and the AM ones are usaully over 100 MMF/PF, so you need to start with an appropriate value trimmer. After you peak each can you can either leave the trimmer in place permanently, or measure the value it's set to with a capacitance meter or bridge, and replace it with a fixed silver mica or an NP0 ceramic cap of closest value. You don't really need to install the new cap inside the can afterward but you can if there is room.
 On those Miller K-Trans I think that the base is held together with what looks like a brass eyelet, I think that you could probably drill it out with a hand drill though I am sure there are other methods. If I remember correctly you can disconnect the two coils from the base, and the compete coil and slug assembly will spread apart and separate from the base. I used to place with a lot of 1950s and 60s era AC/DC radios so I had the opportunity to take some of these apart, Miller K-Trans are only one style, I've even run across some that had a brass shaft attached to the slug, with NPO ceramics inside, and others that were like miniature versions of a late 1930s and 40s IF cans with trimmer caps on top. Why Fisher used the Miller style I have no idea, they weren't the crappiest style of IF can but they were far from the best.
Regards
Arran