Here's a pic of typical plates. There are many out there, depending on what you want to spend. These plates are used in conjunction with the original "clamshell" mounts from the small block. I'm not sure if your V-6 was equipped with them, but I believe the mounting bolt pattern was the same on either the V-6 or V-8.
I have read here on this site that the plates will need to be clearanced a little to clear a mounting boss cast into the LS engine block. Nothing a grinder can't take care of.