The basic need of an iron is to consistently hit the ball and know the distance. Regardless of distance changes, the 718's will be incredibly more responsive with a sweet spot way larger than a quarter, let alone a dime on the 762s. Secondarily, it won't hurt to get fit for a shaft that matches your swing today. As much as "65 is the new 45", there is a physical reality and without some serious dedication to training, ...it won't get better over time. At 67, I'm coming around on that.

64 yrs old with a driver swing speed of 145? Thats in the range of the "top" world long drive competitors. Maybe you should specialize.

I think he was talking about his ball speed with his driver.

I'll guess that it is a 145 ball speed off of a driver head speed of 97 mph. That's still very good at any age. (smash factor of 1.5) and good for 250 yards plus. Short of playing 7000+ yards at the tips, iron distance won't be as important as accuracy. Good news the 718's will likely improve both distance and dispersion when properly fit.

64 years old with a 145 swing speed?! Wow...

My guess is he meant ball speed, or had a typo. I know guys in their 20s who hit 7i 225 yards who have swing speeds far less than that. One guy in particular, who was only 17 at the time "said" he swung driver at 125mph. The pro at my old club did not believe him and said he must be mistaken. So he took him to the range and found out, in fact, that he DID swing at 125. The pro promptly realized he had a rare player on his hands. Next thing you know, the pro decided to coach him for a year or so after having a talk with this kid's father. Last I heard the kid was trying to make the mini-tours, but I don't think he had much luck. Unfortunately, the kid did not go to college and playing mini-tour events was his only path to bigger tours. Frankly, he couldn't control his driver, even though he could hit it over 350 yards. Oh well, I digressed a bit there. Bottom line is I doubt very much the OP meant 145 mph clubhead speed. That's unheard of for amateur and nearly all pro golfers, whether you are 64 of 24.

I did mean ball speed. I don't know much about either, but the young man at the silulator told me that was unusual at my age. We all need a boost now and then.
With that, I hit my 762 5i about 185, PW 145.
Wondering how that would interpret with new irons