the savage 520 was a JMB design. the later 620 just a variation of it. no such thing as an Ithaca 745. shotgunjones is correct in that it was a savage, and was the successor to the 720.

the savage 720 was more nearly an exact copy of the A5 than the Remington model 11 was. I've had 720's and A5's apart at the same time and there are numerous parts I was able to interchange. Remington changed EVERYTHING at least a little.