having trouble locating a crank
Find a shop that's been in business longer than a week, with an employee older than 19.
That is one of the most common ever made, and (unless there are seal etc. differences that I'm not aware of) the dimensions you posted are common to 265 & 283 engines with the small rod and main bearing journals (1955-67), millions of them.
However, you might soon find out that replacing the crank will cost more than simply buying a later SBC engine. Hint: unless you drive with the hood open, no one knows what the engine is.
