D16's! Universal low cost plug for side valve engines. As approved by all my Dennis's and the Merryweathers. Until you have just mentioned it, I was unaware that you could obtain plugs with a built in resistor. I always thought that the resistor was in the plug cap? I am sure that if I googled it there would be a wealth of information on why a resistor is sometimes used, but I always believed that the purpose of the resistor was to increase the RC time constant, so that the rise time of the voltage at the plug tip was increased to reduce electrical interference. As you won't be fitting a wireless to your Peerless cab, I don't think that this will be an issue.