Hi Greg,
I think your plan sounds wise.
I will be eager to hear your report on the mods. The Blue Torii has always intrigued me. I remember forum member Chas used to like to modify them. I was always fascinated by what he wrote.
I wonder if the next larger size of Hammond power transformer might improve the sound. I think of that because of the report BAndrade posted in the Mystery Amp forum
https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1554416974/50 His listener report starts with Reply #58.
He had to build a separate board to hold his new power supply, which in his case is more than only the new transformer. Perhaps the bigger transformer will not fit on your existing chassis and would require an outboard chassis. I would think Steve could mount it on one of his smallest chassis and then mount both the Torri and the power transformer chassis onto a sheet of plywood or something.
Anyway, that is me thinking outloud.
Best wishes for your sound,
Brian