I have not done anything in regards to the pre out, so no advice from me there.
I did recap my 72 twin with the milspec cap, replace the tone stack with double .022 225P spragues and swapped out the 250pf with a silver mica. I can hear the dif. I'm running mine with two 6L6's through a k120 (fwiw).
yes, hand selected means they tested the components to match spec. Without being sure what tolerance was used, the hand spec'd means very little.
As for transformers... the output matters a lot more than the power when finding a source. I'm partial to the tone and the value of midwest magnetic components transformers. They are available from triode electronics.
Across the fender line, the major difference in the great years (ab763 circuit) will be transformers, speakers and power tubes. They will either be 6L6 or 6V6. Speaker differences are pretty easy to figure out and null if you just go with the standard jbl prescription. That leave transformers... and though your pro is pretty similar sounding to a twin, having owned multiples of both, they are not exactly the same... nor is my princeton reverb, but is come damn close to that tone with a E110. The showman is probably closer to the twin in that wattage range... and probably the sf bandmaster reverb is the closest. The vibrolux is probably furthest away, but I think this differention is splitting hairs.
Hope that helps.