The front height is set by the procedure in the FSM, there is no actual body height measurement in the FSM it's a suspension hight measurement. The suspension is set so the control arms are at a certain angle, and the resulting body height would be slightly different depending on the cars wheel/tire options.
The rear height isn't really covered in the FSM, other than using the stock leaf springs it's not really adjustable if you have all factory parts. There was a bumper height specification, you can find it here
The 1970 Hamtramck Registry "Chrysler Passenger Car Bumper Heights 1965 thru 1976" Page
For a '74 A-body most of the specs are here (note this is for '74 so the Barracuda spec is E-body)
View attachment 1716458516
That height comes with the following conditions on how the car was loaded when it was measured
View attachment 1716458517
Cars that are at stock height lower have been lowered can't hang the wheels and tires out past the quarter lip, like you often see with guys running SS springs in the back. There are a couple of cars in the thread so far that you can clearly see the top corner of the 275's is outside the lip of the quarter, so their wheel specs only work if you've raised the back of the car substantially with SS springs.