Heads and rockers

Hi All.
I have two type of pre commando 750 heads:
-one head cast stamped 23166 for spigotted barrell;
-two heads both cast stamped 25319 for not spigotted barrells.
The rockers of the spigotted head are the same with one of the not spigotted head.
The other not spigotted head has another type of rockers; the tube (where you fit the spindle) is shorter (of course the cast of the rockers place is thick).
Two heads 25319, two type of rockers (same spindle for all).
Maybe the head with longer rockers tube is the early post spigotted, and those with shorter tubes is a late head?
Do you know them?
Thank you.
Piero