The 1974 Kennedy Half Dollar is a very common coin as the Mint struck a little over 200 million examples for circulation. The mintage is also more than double than that of the Denver struck Kennedy Half Dollars from the same year. Only in MS66 condition or higher is the 1974-P considered scarce and any example in this condition or higher is definitely worth setting aside.
In MS67 condition it is really scarce with several dozen confirmed. Anything grading higher than MS67 is considered very rare and should definitely be certified.