Ever use a Borgeson power steering kit for a big block Dart conversion?

I can't really make out from the photos, but it looks like those are biscuit mounts. There is latitude to shim the mounts and the box mounting before getting into modifying the headers. The box housing also has lots of material, so you have options to make room depending on your abilities. Also, all the fitting needs to be done at ride height since the is a considerable amount of flex in this area. The clearances change considerably when set on a chassis lift vs. on its weight.