I'm not sure I understand the question, but this preamp is based upon the Bassman topology, meaning that any bassman-derived preamp can be built by altering cap & resistor values. You can literally change everything in there and experiment to taste, but I'd start with the input resist values and the cap&resist values from Source to GND.
As for the EQ, I'd check which kind of tonestack fits to my tastes and change pot, cap&resist values accordingly.
This tool can be useful to this purpose:
https://www.duncanamps.com/tsc/Cheers