The choke space is sort of narrow but tall, skyscraper style.
The choke can be seen to be about the width and height of two 3B28s and there's room above it. Having one of those amps, I've considered the issue of iron replacement before, and am glad I have not had to do it.
The Eldico SSB-1000 appears to have very similar power supply iron in a physical and electrical sense. Its manual is here:
https://elektrotanya.com/eldico_ssb1000_rf_amplifier.pdf/download.htmlJust another sort of potential donor if the parts fit.
Thinking about the choke, IIRC, there are some UTC chokes that are a louvered metal stamped enclosure with terminals on the bottom, air-filled, with an open frame choke core actually fitted inside the box. The S-36 is 4-20H/400mA, and The S-38 is same but 550mA. No idea if any of these would fit, I only learned that the large metal UTC choke box sometimes has quite a bit of air space.