Silvertone 1484 Twin Twelve Guitar Amp Restoration

Had Nick Winnard of  ModdJobbs take care of my 1484 with a complete electrical restoration. It seems my grandfather had made some attempts to modify the phase invert circuit for some odd reason. Anyway Nick restored the circuit to original and replaced old components as well as upgrading the output transformer that can actually do the 60 Watts the amp is supposedly rated for (original transformer was a bit small).

Right now running it cranked channels jumped as seen in the picture, slamming the front end with an MXR Micro Amp. 

So the plan is to work on this amp and getting running proper over the fall/winter for a special event in the early spring. I havent done anything with tube amp electronics before so I'm reaching out on here to experts for some advise on where I should start. 

My own thoughts are: replace electrolytics and then slowly ramp the amp up using a variac over the course of a whole day then to play it, IDK if this is a good idea or not so yeah, looking for any and all tube amp advice!

Side note been chasing the Jack White sound for years with Fender amps and a big muff, this is the final piece of the puzzle aside from a WH-1 :) !