I have one of the GA-5T amps too. I like the tone of it (as compared to a Fend deluxe reverb.)
Years ago, I replaced the dual ganged filter cap ( brown with 2 red wires attached) with a metal one by Sprague. I just took the mounting bracket out of the old position, positioned it around the new cap and used hot melt glue ( or epoxy) to
hold the new cap in a new position - in front of the transformer. I have a black wire, that connects the ground of the can to the chassis ground. The cap is marked: 8 - 20 MFD, 8 - 20 MFD at 450 V. This just means there are two rather
big capacitors, 10 to 20 MFD, smoothing out the ripple on the power supply. The can cap could be replaced with two indivual caps, but since your amp is so minty, I'd attempt to keep it original. This might mean putting the cap back in its original
position, that is up to you. Please keep in mind that the "dressing" of the point to point wiring was done carefully, and with noise reduction in mind, so every little bend of the connection wires may have a purpose. However, on the filter caps, this should not really be an issue; just don't move the red filter cap wires next to the signal wires connecting the tubes! The caps are a little hard to find, but you can get one here: http://tubedepot.com/can.html
CP-CE-20X2-450V ( one of the antique radio repair companies actually makes these caps.)
I don't think of it as a death cap. And I still have a 2 prong plug on my amp. Whatever, do not stand in water, while playing the guitar! { maybe a ground cord IS good - not trying to argue that point...) If you or I DID connect a grounded cord, then you need to be careful to get the polarity of the AC wires correct, because it will usually hum if the hot and neutral wires are reversed. You could check with an AC volt meter, to make sure there is no voltage potential between the chassis, and your house ground... if you are going out and gigging with the amp, then, perhaps, a grounded cord would be a good idea.
I'll have to research a little, to figure out why the tremelo gets stuck...
Regards,
JAM