Hi,
before you start go visit
Hoffman Amplifiers, Tube amplifier parts, tube amps, tubes this is about the best resource for tube amps out there. From parts (transformers, tubes, sockets etc etc.) to forums to to schematics to excellent advice and FAQ's. You may even want to change the amp you will be making.
I revamped my Vox AC30 T/B and inserted reverb. I think you may be well advised to include reverb into the amp now as it will be tougher if you should want to at a later stage.
Contrary to popular opinion tubes are more readily available than thought.
I encourage you to ignore the tube detractors, there is nothing in the rock world that sonically beats playing through a tube amp. Have played through many a SS amp, you cannot get the same from it as you can a tube amp, period. May SS amps have "tube" simulators built in. Forget the specs let your ears be the judge.
Don't be fooled by the wiring, this is the most critical part of tube amps, failing to follow convention will result in hum and crosstalk and other nasty things.
Oh forgot to mention, the voltages are very high and really Biiiite.
Please go visit hoffman amps before you start ........ you will save yourself time and frustration later.
Andrew