How can I find information about the aircraft with registration / tail-number N58644?
I have checked the 01 July 1965 FAA register, and it does not show there. My father had a BT-13A N61907, and it doesn't show either. The usual fate of postwar BT's was sale to crop duster companies; they were of value only for their R-985 engines and 2D30 props to be fitted on Stearman dusters or airshow planes. The airframes were scrapped.

If you can convince someone at FAA OKC, they could call up their archives (in Ft. Worth IIRC) and get the answer you seek.