Original threaded bosses were cut from the donor Grand Cherokee and welded into the inside of the rail where needed. Also shown is the swaybar mount which was welded in from the back side and will penetrate the boxing plate once fitted as well.
Above is the cross member and front engine cradle mounts. They have been mounted in the exact same way as was in the Grand Cherokee. You will see later how they come through the boxing plate so they can be supported and welded on both sides like it was originally.
Next to be fitted up was the donor upper wishbone and coil over mounts. As you can see it does not sit flush on the rail. The pressing here is for extra lateral strength and to clear the coil over. It needs to be recessed into the rail to centre the load more above the rail and reduce twisting leverage. So some plating for the recess was made up. I find it easier to weld them over the actual mount so all the angles are correct.
Before the recess was cut out, I extended the wider flange section of the front of the frame further back. You can see the difference with the unmodified rail behind in the first shot. The extra width was the same as the recess so no strength was lost. The mount was clamped back into place and then the boxing plate tacked in from behind to make sure it was position correctly.
The plate was fully welded in from both sides. The area that would end up of the rail that the mount would cover was coated in weld through primer to help prevent corrosion between the layers.
All angles and the position is double checked against what I recorded before pulling apart the Grand Cherokee. I even have it over the same bit of concrete to keep things as accurate as possible having recorded the measurement on both paper and photos.