Midway between the front and rear axles is the dividing line, fore goes on the front, aft goes on the rear axle, and if there is enough overhang at the rear some may come off the front axle.
For the most part in comparison little weight goes onto the front axle.
If there was a need for realignment with weight in the bed, you would notice this driving without the weight as what is called bump steer, and it would be noticeable, and it would scare you. Very little bump steer or toe movement with suspension movement is designed into the suspension. Some manufacturers do it better then others, Ford twin I beam pre '08 sucks more then most I have read. I know my new GMC ifs drives better then the '99 Ford ever did.
There may be a change of camber with more weight on the front but this also would be little, should not be enough for an alignment adjustment.
More weight on the rear will drop the rear of course, the only effect would be to increase caster very little, again not anything to realign for, it will prob drive better with more caster if set up correctly, more centered.
Whether the camper is on or off shouldn't dictate whether an alignment is needed, I would look to something else.