See http://www.webphix.com/schematic%20h...namps/ga8t.pdf for how trem can be implemented at the power tube grids on cathode biased amps; I can't find any Fender amps that used that arrangement? Feel free to sub in the regular Fender trem oscillator.
For reverb, you may enough tube sockets / controls to fit a 6G15 http://www.webphix.com/schematic%20h...6g15_schem.pdf 'in front' of the 5E3. That's been done on a modern Fender, though I can't find which one at the moment. To avoid replacing one of the 9 pin sockets with an octal for the 6V6 reverb driver, I guess a 12AT7 could be used as per the regular AB763 arrangement.
Vibro King, but it's not a good idea to put 470V on a 6BQ5 / EL84.