If you are still working on this amp, I have repaired perhaps 6 of these and I currently own 3 of them. My experience was that the cable between the reverb transformer and the tank almost always disinitegrated/degraded to the point where it had to be replace. As to the reverb transformer, if you check
Antique Electronics or Hoffman you will likely be able to find a 12K:8ohm transformer. These are really nice little amps that break up nicely at a low volume. The alligator tolex is damn near indestructible and if you replace the old speaker with a more efficient one, this amp has plenty of power/volume for a a small club gig. These are perhaps one of the most underrated/underappreciated/unknown vintage Japanese tube amps out there. They are simply too cool for words.