[Arran]

Grigsby Grunow seems to have been like Rogers, they were not into sparing the steel, most of their chassis are made out of heavier gauge sheet metal, and lots of it. Also, given the design of some of their chassis it's a wonder how they were assembled on a production line basis. Judging by the values of the filter caps,1,  2, and 3 uf, respectively, the filter caps were probably paper rather then electrolytics, so motor run caps, or Solen fast caps, will work as substitutes, and likely outlive you. It's not really recommended to replace such caps with electrolytics anyhow as the modern types in that size will not like the ripple current, I think Terry tried some in a Radiola set, and one of them short circuited within a year.
Regards
Arran