The pots on this specific amp are 22k and 4.7K the closest real world pots are 20k and 5k respectively. These are easy as pie to find.
Make a decision of what is important to you, as for me keeping original knobs is not important so I can use almost any pot, if you want the exact pot I believe it is a 16mm with a quarter inch post.You can go on ebay and see the exact replacement, it is a pc board pot, I hate these, I use pots I buy from a mil surplus dealer and I solder 3 wires per pot to the board and then the other end to the pot, this lets me use any pot I want. Again it depends on what is important to you.
3 turn pots are just annoying for most people because they want a visual reference of where it is set, I don't care about that, I know the amp well enough to know if it needs more mids or less by ear, but most want a visual ref and 3 turn pots do not have this, it is 3 turns from 0-10 but lets me dial the tone in a little finer.
Look up google articles on 808 op-amps and you will find to much info for anyones own use, at 10 cents a piece get as many as you can and switch them out and see the one you like best, for me the differences are in the amount of noise when the amp is set at full throttle, the 353n have less noice the JRC has the best overdrive, the 4558 has the best distortion and so on, just plug and play.
If you want to record this sound into a DAW, that is another set of mods, let me know how you do and feel free to email me email@example.com
I am the promoter for the largest guitar builders event in the country in Miami this April, come by and lets talk solid state anytime.