We needed to fill the OEM holes because the
location of our new Transmission mount was really close to them and
would have given us much weaker mount. We clamped a piece of copper
plate underneath so that we wouldn't have to spend much time on the
underside of the frame cleaning up the hole.
We then ground down all of our body mounts to make
sure they were clean and solid for our Energy Suspension body bushings
that we will be using on the truck.