Question about iron lengths

Although I would defer to a certified Titleist fitter, I believe the standard length of a T150 7-iron is 37". If that is the case, you would order plus 1" over standard length. Keep in mind that the swing weight of your irons could change...hence the recommendation to consult with the fitter.

If the stock length is 37”, then plus 1 inch. Note this will increase the SW, you should specify that to be at D2-D3 (otherwise standard swing weight). Or your preferred swing weight.

Correct!
Standard 7 iron length is 37", so + 1"..........

Be careful. In addition to changing the swing weight, adding 1 inch in length will change the lie angle to 2 degrees upright. I'm 6'2" and based on my measurements, I play clubs 1/2 inch over standard. I have had my club builder add 1/2 inch extensions in used shafts I have bought. I really have not noticed any difference in overall performance.