"...It looks like I will have to grind that down so I can move the box further to the outside of the car. I don't really want to remove it completely, otherwise there's no limit to 'full lock' which usually means something rubs something else and trouble ensues (ooh, matron!)." - @Martin's Eleven (UK)
I don't know if this would apply to your chassis/steering box or if it would be of any help but here is a picture of the 'turn stop' on most all of Vintage Speedsters (Kirk Duncan) here in U.S.