[R-390] R-390 Slugs

[Anthony Casorso]

I have read some archive material and the Collins engineering report on the 390A. From what I have read I have garnered the fact that the 390a RF deck uses exactly two slug types, one for the VIF and one for the RF transformers. These slugs are made from ferrite. That is indisputable because it is so written in the Collins report. Also written in that report is that the 390 used iron powder slugs. But what I can't tell for a fact from anything is exactly which slugs are unique in the R-390. What is the collective knowledge about the R-390 RF deck slugs? 
I took a peek at some R-392 slugs last night and it appears that there are several types and they don't look to me like ferrite. Historically speaking, it makes sense to me that the 392 slugs would be more like the 390 slugs.
The questions arise because a post on another forum is asking for replacement slugs for a 390 but he is not sure what he needs (I think the deck was torn down by someone else and some slugs are missing).
Do we know for sure which slugs are unique in the 390? Do we know if the 392 slugs are equivalent to the 390 slugs (I have some 392 slugs in my junk box)? Unfortunately I do not own a 390 so I can't do any experiments of my own.
Thanks,
Tony