Internal baffles are not important IF (and only if) you only operate with the tank either full or empty.

The weight itself won't be an issue with a properly mounted tank at the front of the bed of an F350 -- the problem comes when the fuel sloshes from side to side during a turn, especially an S-curve or similar maneuver.

When the tank is either full or empty, there is no problem with the weight shifting, but if you go into a turn with half a tank of fuel, the weight will shift to the outside -- the quicker the turn, the faster the weight shift and the more drastic the effects.

The absolute worst case would be a half-tank, and you suddenly need to swerve around the non-driving-fool who just pulled out in front of you or who just had something drop off his vehicle.

The weight is well above the truck center of gravity, so having it shift suddenly can make maneuvers very interesting.