Which part is thicker? My earlier Series vehicles have had radiators with a bigger (front to rear) top tank and large filler cap, but the core itself is only half that thickness, and the later ones have a smaller top tank with small filler cap, but the core is still a similar dimension.
I have had Series radiators re-cored with a thicker core (extra row of tubes) to get better cooling for some of the engine conversions I've done, but that has always been a special order item.