What is the model number of the radio? (It sounds like it might not be the Rigonda-102.)
Rigonda has different tube radio models where the FM tuner does vary a little bit from one another (like L4 is a tapped coil or not).
This is a slug tuned FM module. In my experience (I converted one similar FM tuner to the CCIR band) it involves making new coils, just changing capacitances did not work. Lots of experimentation, as well as simulations, so you better have some test instruments as well. The other problem is, as you identified, that the coverage of the CCIR band is a lot wider than the old OIRT band. I did not achieve full coverage.
The other tube-based FM module I converted was capacitor tuned. It also needed new coils as well as a number of capacitor changes. There I achieved full coverage (88MHz - 108MHz).
Regards, Peter