You can find that slab of steel just laying around on the street.
I use an actual frame head as a jig. I have both l/p and b/j versions.
This one is my mid travel unit with up to 14 inches. It's 6 inches wider and 2 inches forward than stock...
Here's one that I just finished....
And I'll be testing this street version out soon...
There's quite a bit invested in heim joints and will be replaced with conventional type ball joints once its tested and adjusted proper...