All threaded holes in the block and cylinder head should cleaned and tapped with a thread chaser. All bolts being installed should be lubed with a light oil or anti-seize on the bolt threads before assembly.
Disassemble original mount. Discard the heat shield and the plastic isolator.
Clean and wire wheel the paint off of the top and bottom edges of the mounts.
Bolt mounts back together. Weld the long plate to the longer side of the mounts, and the short plate to the shorter side.
We also weld the mount base together with the top side of the engine mounts.