Don't worry about me, I am not familiar with throttle bodies at all.
A true 50mm.
A true 68mm 4.7l
A couple 52mm cores.
96 and up non egr type of vacuum routing.
92-95 egr type of vacuum routing.
Notice the 2 holes for vacuum routing and the 2 smaller holes in the bore as well versus the one hole and the notching in the bore seal. These 2 TB's "breathe" differently through their vacuum routing.
Enlarging these vacuum holes does what?
Holley used several different spring rates depending on the year of the vehicle.
Appears from your pic to have some of the hourglass reduction left in it, at a true 50mm this reduction is gone. Does it still has the stock blade with the "11" stamped on it?