Oh yeah - about min RF transmitters - remember that class C amps are much more efficient than calss A or AB or B, thus you don't need really big tubes. To get 100 milliwatts, even a 6C4 is 'overkill' - it can pump out 2.5 watts at 150 Mhz (says RCA's book). Remember to use a power transformer to line isolate anything you build - and oh yeah, be careful in that Silvertone too. I'd get an isolation tranny for it if it's not line isolated...
Hey, you can download a freebie/student version of PSpice, and if you've got time, download the tube models and virtually model your designs before you build a real transmitter....
Hmmm, I can see (but it's overkill designwise):
12AT7 - RF oscillator + 1 buffer stage of amplification.
12AT7 - AF amplifer (buffer, really), then modulator/output section (think cathode provides the RF or AF, grid provides the other signal)
100V + 6V transformer, solid PS.
Back on topic
When you've got a heat realted problem - you'll find more often than not that it's a capacitor, particularly the wax or 'black beauty' types. Find all of those in your vert section, and hit each one in turn with the freeze spray. But, you'll probbably just want to replace ALL of those paper caps, anyway.