3.5 MHz 2W AM vaccum tube transmitter
It takes a lot of work to make a tank-tuned oscillator stay on frequency; back in the day it would be a project in itself, in a separate case, so that you could use it on multiple rigs.  I'd use a crystal.

Getting a pure tone out of the oscillator isn't terribly important as long as your signal is pure going out the antenna.  If you're running a class B final then you'll need all sorts of harmonic filtering anyway.

If you really want to go old-school, go with a class C output stage and modulate its input power.  But don't ask me for help -- that's getting above my pay grade!