The Red Llama by Way Huge is a great tube-like overdrive with plenty of output. I've drawn 3 layouts–one for every typical Hammond box! The 1590A layout uses 9mm pots which you should be able to board-mount. The other 2 use typical 16mm pots. Make sure to use the unbuffered CD4049 or else the circuit won't work.
This is a library of perfboard and single-sided PCB effect layouts for guitar and bass. I'm not an electrical engineer by any stretch of the imagination, just a DIY'er who likes drawing layouts. It is meant for the hobbyist (so commercial use of any of these layout is not allowed without permission) and as a way to give back to the online DIY community.