[Arran]

I would consult Shango066's channel on Y.T, he has multiple videos where he replaces the caps inside the cans, now he usually uses one of those cheap component testers to measure the values. As you surmised the caps are sandwiched in the base of the assembly that is held together by the brass eyelet. They are not all the same value, which is why they should be measured, if you are lucky you may find a posting somewhere by someone who has already restored one of these sets, but there is no guarantee that yours will be the same, but likely more on point then chucking 110 pf caps at everything. As I mentioned, if you tried aligning the IFs and still had poor gain, open mica caps is likely a cause, the mechanical connection between the silver deposits and the outside world is not exactly the best, plus it can tarnish. Some people have actually fixed these by dropping the sheets in Tarnex (silver polish) but with NP0/C0G caps available, and inexpensive, I think you would have to be desperate to do it.
Regards
Arran