Plugs you say.
BCPR6E
They are a NGK V-groove 0.8mm gapped plug.
Thats the exact part number, don't go adding bits to it or changing it. They can be had from Motor traders/Coventrys for as little as $2.80 per plug. Buy else where and they might not have them and if they do you will be looking at $4.80 or something per plug.
Under full load/WOT... Have you checked your voltages? Maybe your Alt is on her merry way?
Has the motor been out of the car? Check all earths. Battery to chassis, battery to chassis to motor, all the little earth straps from the chassis to exhaust manifold, inlet manifold and head. Lots of little buggers around. Well there is on mine.