I did the same thing except used an old socket for the top. 1 1/4" X 1/8" thick flat bar is perfect. Be careful though, I made mine using the old nuts to get the correct spacing, but had some new nuts also and they were slightly bigger and did not fit my socket.
Here's the link to the post where I describe making the socket.
There's a New BJ70 in My Garage!
Here's the link to the post where I describe making the socket.
There's a New BJ70 in My Garage!