I may have misunderstood what you meant...
Those resistors attached to the output tubes, the ohm value is between 47 and 50 ohms, and I agree that it isn't critical which value you use. Sunn varied between the two values.
However, the ones attached to pin 3, the plate are rated at 5 watts. Only the ones attached to pin 4, the screen are 2 watts.
If you replaced the 5 watters with 2 watters, then you will more than likely blow them if you use full output.
All of these resistors are supposed to act like fuses - to blow when too much current is drawn by the output tubes to protect the output transformer. Too much current can result from a bad tube, one that becomes internally shorted, or a sudden loss of bias.