Here's all the BYOC mods for Proco Rat Clone if any of it helps.
LINK HEREI'm building a couple heavily modded rats myself. They're gonna have the Ruetz mode, OD mod (added clipping stage with dpdt toggle), 3 way rotary switch for the stock diode switching (stock, LED, bypass), a feedback loop on a spst momentary footswitch and a feedback pot and lastly, I'm thinking of adding an external bias pot with an on/off switch. Not sure about the bias pot though, need some experimentation.
aka Dead Eye