Now this is where there may or not be something wrong with the speaker replacement: Was the original field coil used as a choke in the power supply or not?
In general terms, there are 2 types of field coil speakers that can be considered either high or low resistance. Low resistance types will measure in somewhere around 100 ohms and are wired in place of a power supply choke. If the original speaker was one of this type, then the power supply would either need a new choke or a power resistor to replace the missing field coil.
The high resistance types will measure in the 1000's of ohms and will be wired across the power supply from the high voltage to ground. If the original field coil was one of this type, then the wires can just be unhooked and insulated, with no need of replacement.
So, where do the additional wires on your amp go?