Here's the total list of things you can change from the standard build.
1. Toshiba transistors on the shunt, they tend to be closer matched than the alternatives.
2. Replace the j310 with J113, slightly lower nose.
3. Replace the J107 with 2sk170, if you can find genuine parts.
4. Fancy resistors for cart loading.
5. Some fancy bits for the RIAA stage, any resistors and almost any caps. 18k2, 147k, 11n and 33.3n. But bear in mind they need to be matched down to 0.1% so forget anything like boutique film caps, you'll simply never get them to match closely enough. Stick to styrenes and small film foils, larger film foils unless counter wound will add inductance.
The v2 and v3 are to all intents and purposes the same boards, there's no difference to sound.
You can go to town on the PSU if you like. I'm not saying there would be an audible difference between using £6 common mode chokes and having Lundahl wind you some in silver foil to the tune of £300 each but you could do it if you wanted. One area where you can improve it is the earth arrangement. It's quiet in stock form with no earth lifts but if you fancy you can link up every chassis/common contact point with a DDRC so you leave just one unbroken earth path through the whole thing. it sounds fine without it, but there's always the tweaking.
And of course there is a new output buffer board the Calvin buffer which is intended to make it a better driver of long cables or into low input impedance amps down the line.
Kuzma Stabi/S 12", (LP12-bastard) DC motor and optical tacho psu, Benz LP, Paradise (phonostage). MB-Pro, Brooklyn dac and psu, Bruno Putzeys balanced pre, mod86p dual mono amps, Yamaha NS1000m