383 sits crooked in engine bay

Looking at your pictures of engine mounts engine side. The driver side looks to hang lower. Looks like taller ears would hit pump. The DC style k member moves that part of the k frame mount back. Giving oil pump room.
So the hole in the mount or the trimming of the ear may be necessary with that conversation mount. You could possibly die grind the saddle on passenger side to lower as well as raise driver a little depending on the existing height.
I think it's Schumacher type mount so a few people on this site should have actual experience with this mount.