Re: Capacitor value question.
The first high quality amp I ever owned was a Risson ETA 80 (I think that's it). It had two 6550's, and I got it from a pawn shop in Redondo Beach, a few miles from where it was made, when I was 15. Back then, I knew nothing about tubes or hand wired amps. I just knew it was a poor man's Marshall that actually had more gain than a JCM 800. Now, I know it was literally a boutique Marshall.
Even Slash was hip to them, since they were local. His first good amps were Rissons too.
It's cool that you have one, and can upgrade it. I wish I had that amp I paid $240 for. I'd appreciate it much more now.
In 1987, I had just gotten a Jubilee 2555, and also had the Risson and a Carvin X100B. Those were the 3 heads I had in my late teens when I started playing in bands.