I suppose it depends on how much retrofitting your willing to do. I'll assume you plan to do whatever is needed since you didn't give any mounting info and you plan to change the rectifier design anyway. Also, you only mention the primary voltage requirements. Of course, with the PT not working you don't really know what the seconday HV is.?. I've read that the HV on those amps is really too high for el84's. So I might suggest this is a good time to change that. Even though it will mean a small change in tone. Lot's of el84 amps out there doing fine at around 400Vp so that's what I'd aim for. I'm a Hammond guy myself. But Hammond doesn't make a good PT for this. Their offering would be the 300DX which means you'll have a couple of unused taps and secondaries. Which means extra size and weight. Since Hammonds are often larger than other transformers anyway it could be a cumbersome retrofit. Also, the HV is a little low at 550V CT. But if you look around I'm sure you can find something from another MFG. You probably want about 570V to 580V CT to hit the 400Vp spot with a full wave rectifier. Probably good for better than 100mA on the HV secondary and at least 4A for the 6.3V secondary.