The other day I saw a tweet mentioning @guitarnoize demo’ing long time EffectsBay.com friend @cubisteffects ProCo RAT modification called the Four Headed RAT. Basically, it’s a modification that provides additional voicings (two overdrive and two distortions for four overall voicing options). Along with the voicings, he replaces capacitors, ICs, and DC Jack. Christian at Cubist Effects also offers a ‘noise’ mod as well.. which gives you additional noise/feedback, etc.
Basically, you send him a ProCo Rat, you pay for the modification, and get back the four headed RAT. Check out his pricing here.
Below is a great video by guitarnoize which goes into great detail of what this pedal can do. Very cool.