Below is a preliminary drawing for a 4-1000A grounded grid amp using two tubes also with the Eimac specs.. My plan is to drive it on AM with a screen modulated 4-65A driver outputting around 65W to 85W max into it. At +3000V it will increase the needed drive power which is good and also lower the input Z closer to 50-ohms. My goal is to get around 750W of AM carrier output from the 4-1000A's. I'm hoping the control grids and the screens can just remain grounded to where all I have to do is adjust the cathode current and regulate it when static. Another thing I'm going to do is connect the filaments in series and double the 7.5V to keep the current on both tubes identical and equalized. The other benefit of doing that is it will greatly reduce the current needed to heat both filaments. It's possible it could alter in input Z just slightly, but I don't forsee any real issue. .