OK... I don't know either. Maybe someone will recognize the box and can put a manufacturer to it.

You have to look at the firewall as well as the overall construction of the airplane. To me, seems a 61 would be perfect for a 55" wing span. I usually go by this rule. Does the motor fit inside the cowl. If yes, then next, can you properly balance it with a bigger motor without adding a lot of weight? If you can, then go with the bigger motor. Getting the proper CG is would be the only limit on oversizing an engine in this size of a plane (if it's built or reinforced strongly enough).