Here's a pic - not mine and not very good quality, but it gives you an idea. Typical DARKVOICE: very neat point-to-point wiring, and a very simple, "full direct coupled curcuit."
The most obvious mods are the valves. I've already ordered some SVETLANA 6S19P-Bs (10 for $18.99) and there more generic Russian equivalents, the 6S19Ps. These are more durable, mil-spec versions of the 6S19 (6C19). Also bought 5 Philips/Mullard black-plate 6AK5W, a mil-spec version of the 6J1 (other equivalents 5654, EF95, 403A, 6F32, etc).
This amp also seems to appreciate a really good power cable - I hooked up the QED Conduit and it improved the sound quite a bit.