Don,
I would stay with the original 12K as the designers intended. This resistor will dissipate considerable power if excitation is lost as the clamp circuit goes into operation thus requiring a high wattage rating.
A modification isn't going to affect just one aspect of operation but unfortunately many modifiers ignore this simple truth. The Valiant/Valiant II work fine on all modes with the existing 12 K resistor.
While working on your Valiant II I would suggest loosening the set screws in the flexible coupler that is part of the VFO drive. As you know the Valiant is very heavy and when the Valiant is upside down and resting on the top of its front panel the flexible coupler will try to hold the panel rigidly in place and generally it will lose
The coupler can be repaired if broken but it is not a standard replacement item because the input and output shaft sizes are different.