The only real changes in the pics are carbon comp resistors and different coupling caps. The choices for elytics are pretty standard amongst boutiquers and homebuilders. And the pic doesn't tell me if the transformer is different.
Those couplers aren't Mallory caps. TAD -- tube amp doctor. http://www.tubeampdoctor.com/en/shop_Capacitors_TAD_Mustard_Caps/
They're like Sozo caps, trying to replicate the traditional Mullard Mustard caps. Not necessarily good from an audiophile standpoint, but they do sound good in guitar amps. Most polyester film caps give a sort of sound you know since mustards were what was used in classic British amps. The difference is really subtle, of course.
There's a lot of debate about those resistors, too. Modern carbon comp aren't quite the same as vintage ones, and for all the difference the resistors make, carbon comp introduces noise because the places that make the most difference are also the most sensitive to noise, like plates. Lots of us use carbon film as a compromise, or some really neutral metal films like PRP. In this amp, I don't think you'll get any advantage replacing the resistors.
Just my opinion -- and it's no more valid than anyone else's -- but when looking to upgrade amp tone you get a hell of a lot more change out of a different speaker choice than anything else. A good output transformer will do more for your tone than caps (Assuming you have decent caps in the first place) and caps will do more than resistors. Both caps and resistors will be pretty subtle and subjective in this amp unless you start changing values to tailor the tone.
All that said, if someone gave me one and I was interested in hearing the difference, I'd probably gut it just because I like tearing things apart. I could build a clone of that P2P circuit in an hour with parts on hand.