What to put between frame and conv. plate?

[kevinc]

Here's a better picture of the cross member and the location of the frame mounts. The previous owner said he had a small block in it, but he said lots of things just to find out he didn't do it. He may have had a I6 in there for all I know.

I also included a picture of the type of conversion plate I'm using.

I would like to have the engine sitting farther back if possible. Please advise.