200R4 update

I used the TCI adapter. I would have to measure to be exact, but I would guess 3/8" I mounted everything together and sprayed some paint around the block onto the adapter plate and then cut it to fit. It is billet and was a ***** to cut, but once it's done, you will have the size you want. Look at reply numbers 61 and 76 for pics of the adapter plate and the cut down version. If anyone really needs to know, I can measure the thickness.