A couple of ways of doing this.
    You can buy conversion spacers that take you from 4 lug to 5. They generally add about an inch to track width which is a bonus on the back of a Sunbeam…but can be a big issue for the front as the wheels may stick outside the guards oor touch the lower front valence on lock.

    You can redrill the existing hubs… But have to space carefully.

    Final option is to turn up some new hubs.. iirc Doug Jennings or maybe Tom Hall had made some blanks.