I did the mod on that Tad 60 amp and it was fun. The deep cab actually looks quite nice live as the pics don't do it justice. A separate power supply is also a good idea with additional work needed. This was my biggest and most complete amp project to date as I am learning. I was lucky enough to,have a well regarded builder outline the best ways to improve this amp. I learned a great deal from him and this project.
It was a lot of work as I basically replaced most every part except the trannys. I added much more capacitance and instead of the power resistor used a high quality choke for a robust Pi filter. I like to use the large can computer grade capacitors in power supplies combined with chokes. Do not use bypass caps on the large caps as it closes in the sound and sounds a tad unnatural.
I also used solid core copper wire for better sound. As far as the coupling caps go I used Mundorf SGO and if I did it again I would use JB JFX premium film caps instead. I would use these everywhere I can as they have values up to 47uf! They sound better than the SGO's and cost 1/10.
Ya, they are that good.
Bypass the Alps volume pot as it is not that good. If you must have a volume control in the amp, then use a nice Gold Point stepped Attenuator.