I recently purchesed an old Ho standards gauge. I was wondering if the older the gauge the more absolete it is because I was reading the instructions and it said 1963
Try checking the NMRA website. I don't think there have been any sustantial changes. Just type in NMRA and you'll get the official website. You can compare dimensions.
I don't think the Standards have changed in that time. Finer wheels are not Standards but Recommended Practices (which is why it's RP25, not S6). Certainly the layout of the gauge hasn't changed in all that time.
Mark IV is what you'll be looking for. The IV has clearance checks for stacks, and high cubes, plus they moved stuff around, such as the go-no go (for wheel checks)...