I don't have all the measurements for you , but here's a couple of pics that might help you form an image of what it should look like :
Side / bottom :
The bottom of the support has a groove that's about 3/8" wide and maybe 3/32" deep . That groove runs the full length of the support .
End :
You can see how the front is supported via a single bolt with locking nut . The rear of the support simply slides onto the 1/4" square 'tongue' that's welded to the flat under 'rail' .
Sorry , that's all I have right now .
Pete .