John, I've been fabbing my own frame to body mounts as I go, it's quick and easy.

I use 2x3 or 2x4 inch box tubing, with the length cut as needed and then sliced diagonally to make a matching pair of them. Then drill your holes accordingly.

Here's the only picture I have handy, ignore the tube in the picture, I'm using it to hold the body up off the frame while I cut on the rear. I removed the tube, set the body back down over the frame, and tacked them to the frame.