[MrFixr55]

Hi Dan,

Yes, replace the entire present tone circuit with a 0.005uF cap from the plate of the 6F6 to its cathode (at chassis ground potential.

The variable portion of the tone control moves from its present location to a 0.005 uF cap and a tone control potentiometer (I think about a 500K audio taper pot will do).  The connection is simple.  One end of this 0.005uF cap connects to the triode plate of the 1st audio amp or to the grid of the output tube.  The other end goes to the leg of the pot that the wiper touches when full CCW. (This is a correction from my previous post.)  The wiper terminal goes to chassis ground.  As a comparison, here is the Audio section of a similar set, the Philco 41-240:
   

The control can be mounted in the hole previously occupied by the tone switch.  This will allow for continuous variation instead of the switch which provides almost no treble attenuation vs too much attenuation.

Hope this helps.