Pushrod length help

Question - for Cup style pushrods: When a vendor like Summit or Jegs etc say "7.389 in. Long" Which length are they measuring? A or B?
I was told to measure from the ball end to the bottom of the cup. So I had to measure the depth of the cup then subtract that from the overall length to get to the length needed to order a set from Home - OE Push Rods - Manufacturer & Distributor.

If you read a lot of threads you will find that few if any have had luck using off the shelf pushrods with 273 rockers.

I made a measuring tool by cutting piece out of a wrong-sized original pushrod and tapping the two remaining pieces to join them with a piece of 1/4"all-thread with a locknut.