The chains are much stronger today so this should not happen! 530 o/x-ring chains will withstand a CB750.
Like D.I.D 530 VX, X-Ring chain for CB750 std or modifed. My K2 project with less than 80 rwhp will get that one.
I use stronger version since my CB750 K6 has over 90RWHP. +80RWHP when I mounted it.
I have the stronger D.I.D 530ZVMX waiting to replace my DC chain that hardly will snap and has not stretched anything what I can see after about 9000km, mostly hard acceleration.
I guess that a bad/wrong done riveting of master link can cause problems