So, I finally have it. All we ended up replacing were the filter caps on the power end. The shop checked everything else out and it all looked good - tubes checked out good.
The clean sound on this is marvelous. SG straight through the vibrato input and out through the Mesa cab, is just wonderful. Very sensitive to pick attack and pressure. And it shows me every mistake I make.
There's a hum when it's just idle that I'll have to figure out. It's not terrible and I almost wonder if it's just the way this amp is. The Fender DeVille I had had a slight hum to it as well. But the vast majority of the hum can be dialed out of it with a drop in the treble.
Also, I'm going to have to get an RCA footswitch for it.
At any rate, it's in pretty decent shape for a '63, I think. Here's some actual photos from this evening.