My bad: there is a choke, it was just hard to see until the chassis was out of the box.
It's + lead was mechanically broken loose from the board which was likely the source of the rumbling/ oscillation. The caps were all 40u/450V. 4 in series/parallel for the plate node, then a choke, then 2 in series for the screen, then another for the preamp/PI/vibe.
Trem isn't working. Any idea what the problem is? My first guess would be the caps, which are mostly tropical fish caps. Is there a color code for them like there is for resistors?