A vehicle with A-arm front suspensions starts off with a slight amount of negative camber (i.e. wheel pointing inwards at the top), strut suspensions start with a bit more. As you go into a corner and the outboard suspension compresses, the negative camber of the outer wheel with respect to the body increases (strut suspensions gain less than A-arm types therefore the greater initial setting.) At the same time the vehicle is rolling outwards with respect to the road which reduces the negative camber. If everything is set correctly, at the limit, the tire is exactly perpendicular to the road surface giving maximum contact patch.

Sway bars reduce body roll and transfer more weight to the outside tire which reduces its adhesion to the pavement. A front sway bar will cause a vehicle to understeer more, a rear will increase oversteer. By reducing body roll, sway bars allow less initial negative camber; this increases the contact patch in a straight line and shortens braking distances. A vehicle with very stiff sway bars may be slower at the limit than one with softer bars but it will probably be more predictable and much easier to drive at or near the limit because the bars tend to reduce the abruptness of the understeer/oversteer transition.

All this changes with an F150. The low angle swing axle front suspension (AKA Twin I-Beams) requires that you start off with zero camber. (The very last thing you ever want to experience with a front swing axle is the transition from negative camber to positive camber. It results in an instantaneous and ever-increasing loss of traction.) As the outboard suspension compresses in a corner, there is a very slight increase in negative camber with respect to the chassis. At the same time, the body is rolling outwards; when it does so it lifts the inboard end of the swing axle by an amount equal to the body roll which adds lots of positive camber. The harder you push this kind of a suspension system, the less traction you have in a corner as the contact patch gets progressively smaller and smaller. There is never the gain in contact patch with increases in cornering speed that you see with other suspensions.

When you add sway bars to this setup, they reduce body roll just like on normal suspensions, but rather than decreasing the rate at which you gain contact patch, they decrease the rate at which you lose it. They still transfer weight to the outside tire, so the loss of tractive force and increase in understeer is still present but it is offset somewhat by the fact that the tire is now retaining somewhat more contact patch. On an F150, the sway bars do not allow for a change in initial camber settings that would enhance braking; the initial setting is zero so straight line braking is already optimized.

The net effect is that sway bars will have more of an affect on F150s than on most other vehicles. BUT look at the vehicle that you're putting the sway bars onto. It features a high center of mass which in turn is located high above the high roll centers (the geometric point about which the suspension moves) which in turn are constantly changing with body roll This is a recipe for poor cornering. Ideally, you want the lowest possible center of mass and roll centers which are both lower than the swing axles allow and move as little as possible with respect to body roll and suspension movement.

Add to this the terrible weight distribution of any truck and the handling limit should not even be a consideration. You have a very heavy front end which starts with a massive amount of understeer and tends to lose traction as you push cornering speeds. This sounds like it should make for stable but somewhat slow cornering. It would except for what is going on in the rear.

In the rear you have extremely stiff suspension relative to the unladen weight. It compresses very, very little in cornering and transfers most of the weight to the outside tire with very little provocation. The addition of a rear sway bar only increases this tendency. When pushed to the limit, the rear suspension is likely to give up traction more suddenly and more totally than the front.

So when you drive it hard into a corner the front end begins to push more and more until it arrives at some sort of a steady state determined by body roll, contact patch and speed. At that point the vehicle will begin the understeer to oversteer transition which all RWD vehicles go through in a hard corner. The transition is sudden and can be violent. Once the oversteer begins, it may not stop. If you make the mistake of lifting off the throttle to try to regain control, the rear end can snap around almost instantly and no amount of counter steering is likely to save it.

The bottom line is: it's a truck. It's not meant to be cornered anywhere near it's limit.