Overheating -- Corrective measure questions.

Kent mosby said
I have sent a message to Cold case radiators and asked about their recommendation since no scamp or valiant came with a BB motor.

Would it be beneficial to open the core support opening by 2 inches a side to fit a 26 inch radiator?

Not in my opinion, no. You'vet got majority of the core exposed. So all of the water going through it will be exposed to airflow since it's moving. It's up to you. Some do it and some don't. I wouldn't.