These images of Vicente Bañó (which in English would be "Vincent Bathroom"!) are all from within a few years of I sette gladiatori. I don't see much resemblance with the guy in 4/8, but I don't see him anywhere else either.
Since the opening "gladiators in prison" scene features Bruno Arie and Pino Mattei then I would assume that it was shot in Italy, so chances are the actor in 4 & 8 would be an Italian.