Back some years, when I put the 466 SCJ in my Pinto, I used both a front and mid plate that I got from Jack Roush. Made of 3/8ths aluminum, I set aluminum tubes through the bottom outside corners. I got heavy wall rubber hose with a 1/2 inch ID, and found another piece of hose that the first one would slip into. That whole construct fit into the tubes welded fore-'n'-aft into the plates. Brackets on the frame were placed so as to just have the rubber-lined tubes fit into them with a chunk of tire sidewall in front of, and behind the tube so there was no metal-to-metal contact made by the 1/2-inch bolt.
The two thicknesses of hose made for a bit of 'give' and dampened vibration. Front and mid plates carried the weight of the engine, and with a regular trans-mount for the C6 on a removable crossmember let into the frame, it worked just fine.
I intend to do about the same thing with my present project, when I get to that point.
KS