I replaced them with 40 uF 500V caps I had here. B+ is rock solid. The transformer is now properly mounted, and still motorboating. And the specs of the transformer exceed those of what the radio had.
Here's the schematic:
http://bama.edebris.com/manuals/national/nc183d/
The radio screams loud even in "standby" mode, which I assumed shut off the B+??