I'd be inclined toward laying the base of the tines over something like a concrete foundation block, with the handle wedged under the front tire of the truck. A spare chunk of water pipe just large enough to slip over the tine, and at least as long as the fork handle should provide enough leverage, since the leverage available to produce the bend was the fork handle.

The advantage of this rig is that the tine will bend at the end of the pipe, where the load is applied locally at a fairly specific point, so by sliding the pipe on/off to the right point, you can straighten where the bend is, rather than just deforming the whole tine to a "differently bent" kind of misshapeness.

If there's a lot of springback, you may have to use two blocks, but be careful to assure that you have an appropriate landing place when the fork twists, the pipe slips, and your ass hits the ground. And don't wrap your fingers around the pipe so that they'll get pinched when the fork twists and your knuckles hit the ground (abnormally). It will hurt.

John