If memory serves, the Savoy has the 12JP4? If so, then in going to the 12LP4 you need to add an double field ion-trap, change the anode connector, and make sure the dag coating is grounded. The 12JP4 doesn't have this coating, supposedly. You need to be able to accommodate a slightly different bulb diameter.
http://tubedata.itchurch.org/other/S...Manual1953.pdf
John