I have a 59 f1 with a 223 and 3 speed and I changed the axle ratio from 3.70 to 3.25 and I need to know what tooth speedo gear to use thanks

 

Idrive, welcome to the forum. Your question is not as straight forward as you might think. 59 F100's didn't offer a 3.25 differential and if your truck is riding on different sized tires from stock, then you will need to consider that also.
Good luck in your quest.