Pushrod length help

My build:
1975 360 LA block
Speedmaster heads
Custom grind Comp Cam from IMM engines: 234/234 Duration .533 Lift HFT, 108 LSA
Howards Anti-pump Hydraulic lifters p/n 0424
Stock 273 Adjustable Rockers on banana shaft arms

Looking for pushrod length to order but im curious if anyone has suggestions on best way to find the right size.

I grabbed the wrong double round ended pushrod measurement tool to install on a fresh lifter and tried to figure out where the base of the cup would be.

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?

Thanks in advance