Well, the problems are, the front spindles have different spindle geometry than the later generation ('67-'6
and there will probably be some handing issues if you use them (bumpsteer, etc)
I can't think of any parts that will exchange exactly - the pitman arm on the '66 is smaller than the '68, and lots of various little differences will make things not interchange. The PS pump will work for any of them, and the Control Valve should interchange, but not the ram, not the draglink.
Sorry they don't interchange as well as you might hope, but there are a lot of '67-'68 cars out there.