Getting the truck to tow level is not a requirement for proper WDH adjustment.
Equal-I-zer states:
Good adjustment:
You have most likely achieved good weight distribution adjustment if your measurement on Line C of the weight distribution setup table shows that front wheel well measurement is at least halfway back to the original uncoupled measurement. See Line C on Weight Distribution Setup Table (p. 16) and Figure 19 below. It should never be lower than Line A.
Equal-I-zer does not provide any specification for rear-end height -- only for front-end height.
When they say, "It should never be lower than Line A", they mean the front-end load with WD applied should not be more than the unhitched load.
If, by "level", one means the front and rear ends should drop by the same amount, it would be necessary to transfer excess load to the front to cause it to be lower than its unhitched height.
Equal-I-zer also states:
If C is LOWER than A, you need LESS weight distribution adjustment. See Line C on Weight Distribution Setup Table, Figure 14.
Over-adjustment is a very dangerous situation where loss of control and jack-knifing is possible, especially in wet or slick road conditions.
Ron