Whew! This certainly is an interesting one. If I didn't know better, I would say you have steering linkage from a power steering car underneath. And that up and down movement! That means you can move it side to side the same amount. Wow! Best advice... Get a new front end. I don't know what kinds of steamroller tires you guys are running or what you've got your alignment specs set to, But steering gearboxes are overly designed for the application. I have seen many P/S boxes go out (integral) because of loss of fluid, but manual steering gears... Rare in my book. And what the early Mustangs have are manual boxes with power assist. Hope you figure it out soon... the way it sounds, I suggest you don't drive it.