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.
Remove old engine mounts from your big or small block engine. Mount one plate per side on the older engine. The Retro conversion plates are marked "D" for drivers side, and "P" for the passenger side with both arrows pointing forward. Torque these counter sunk bolts into the block at 28 ft. lbs.
On the drivers side of Gen III and Gen IV big block engines you will be required to trim the bottom rear corner off of your factory LS engine mount.
Install your factory LS engine mounts using three bolts per side and torque to 28 ft. lbs.
You are now ready to install your engine into your LS engine compartment. These adapter plates will move your engine back 3/4 of an inch closer to the firewall. This will improve the position of your new engine. LS engines are completely flat on the back and if you retained the original position of the transmission it would put a large gap between the back of your new engine and the firewall.