The '71 Charger has a 20-gallon aluminum fuel cell/tank with foam. It is pretty basic tank/cell, not one of the Fuel safes that are designed to stay intact in a crash (internal bladder, shielded.)
For racing, there are some rules. Because mounting the cell high above the rear wheels will help weight transfer on lunching the car in drag racing, Per NHRA, the top of the fuel cell must be below the top of the tires. With a high mounted cell, side-to-side cornering / handling will be less stable than if mounted lower in the car.
In straight line acceleration, fuel slosh (no foam) is not much of a big deal, unless the fuel pickup is uncovered.
In a car designed for handling/cornering you don't want fuel slosh, and moving the cell closer to the center of the car helps more, but most old cars would need major modification to have the cell located under the passenger compartment. Many newer cars locate the fuel cell below the rear seat area (under the floorboard) for better handling, weight distribution, and protection from rear end crashes.
Remember that the fuel is moving dynamically from the vehicles acceleration forces. Having a large high mounted, unbaffled, tank/cell behind the rear wheels can cause the rear end to kick out like being hit with a pit maneuver, if all the fuel sloshes to one side quickly.
Part of the fuel slosh issue is with a full tank, it is heavy, but there is no room for the fuel to move, so not much weight transfer side-to-side, but 1/2 full the fuel can change the side-to side weight going around corners quite a bit depending on the volume and the width of the fuel tank.
Think long, narrow, short is better than wide, short, and tall for a handling vehicle.
And, yes, I spun out (and flipped) my 1985 RamCharger going around a corner too fast. 1/2 tank or a bit more fuel in the 35-gallon unbaffled tank located behind rear tires on a short wheelbase 4x4. That is over 100 pounds of fuel sloshing from side to side.
A bit more dynamics going on in the accident. At first making the left hand turn with too much throttle (OK, I was drifting the truck a bit), and when I went to correct by turning right all the fuel that was at the right side of the tank quickly sloshed over to the left side of the tank, and the back end if the RamCharger kicked out and kept going left to where the truck spun a 180. While on the brakes sliding backwards (almost stopped), the left rear tire caught a curb, and the truck tipped over on its side.