Nice DYI swap!
The counter guys at every 4x4 will prescribe the same Rx when you mention bumpsteer "you need a different pitman arm", but that's the bullshit one-trick pony answer.
A dropped or longer pitman arm is often the answer when raising a truck, but a Ford van's steering box location and angle is so different, that swapping out the pitman arm hardly changes the bumpsteer condition.
To improve things, you have two goals.
1) get the drag link and track bar the same length, and same angle.
This makes the axle housing move in the same arch as the drag link when the suspension cycles, which minimizes bumpsteer
2) get the drag link (and track bar) as parallel to the ground as possible. This location places the drag link at the center of it's arch, again, minimizes bumpsteer. You can achieve this by doing the 'cross over steering mod' to the passenger side knuckle. There's a machine shop in Redding, CA that offers the arm and service, so does Ujoint Offroad, who did mine for me. It's precision machine work, you want the type of arm that both bolts, and is keyed into the top of the knuckle, you need a milling machine and skills to pull off this DYI. Or just mail your knuckle in, pay the man and get it done, which is what I did.