[quote name='samhay' timestamp='1482256818' post='3198999']
The rub is that your preamp almost certainly won't use 250k tone pots (looks like 50k or 100k), so you will lose some range (brighter settings) as finding dual gang pots with 2 different resistances is not easy.
[/quote]
It's fairly easy to make one, buy a dual ganged pot of one of the values and a single gang pot with the other. Take the back off both pots and replace the carbon trail on ONE of the dual gang wipers with the second value (from the single pot) and reassemble. You'll need a flat blade to prise the clasps off the back and some pliers to refasten them, but other than that it's fairly easy. 😄