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The physics of moving the battery are more dramatic than they appear.
The front location is forward of the front axle, which means that the 70 lb. battery exerts more than 70 lbs. on the nose - by cantilevering, it removes weight from the rear axle.
The change to trunk mount is exactly the reverse: since the weight is behind the axle (and probably far more distant than the front location) it adds more than 70 lbs. to the rear axle weight since it removes weight from the nose.
The actual numbers can be had by measuring the distance from the center of the battery to the front axle, divided by the wheelbase, and multiplied by the battery (and tray) weight.
Example: if the battery center is 11" ahead of the axle and the wheelbase is 110", the ratio is 10%, so you get an extra 7 lbs. on the nose.
Do it the same way for the rear. The battery center is 20" behind the axle, the ratio is 18.2%, so the change includes:
1. the 70 lb. battery
2. the extra 7 lbs. on the nose
3. the extra 12.7 lbs. on the rear
totaling almost 90 lbs.

The rearward distance also helps prevent weight transfer slightly by increasing the polar moment - the leverage makes the tail end harder to rotate around the axle center.


Assuming your numbers/calcs are correct and they seem to be and I agree with the conclusions, there is another impact to consider besides just a straight line forces one might consider in moving a battery, a rear mounted battery can be mounted often lower, lowering the COG, and if any cornering/handling goals are desired, there are some benefits to be found having a battery in front of rear axle, closer to f/r COG regarding yaw forces.



And of course its not just about fore/aft distribution or COG

Placing a heavy battery over or behind the right rear wheel adds ballast where it's most needed - because its the RIGHT side wheel that tries to " pick up" due to the inertial counterforce of the pinion against the crown wheel.

(Same reason a single spinner always breaks the right tyre loose....)

Placing it over the left rear wheel CAN cause more potential loss of traction due to the existing imbalance of downward force between the left and right wheels....but this is when the car is on the ragged edge of tractibility.....

Generally the battery re-location is one of many mods like a snubber, stiffer right side spring, spring clamps and rated shocks that go towards correct weight distribution and achieving separation which the Mopar leaf spring system was designed to do.

Bare in mind...a lot of these adjustments work because the super stockers ran serious overhang behind the wheel arch - a short assed car like our aussie Chargers usually needs some sort of traction bar or Caltrack.

Squatting is for chicks and Chebby owners