Problem with replacement Idler Arm
The mounts difference is obvious. the older mounts are a square/ rectangular "pillow mount" and the newer "spool" mounts have a large bolt going through from front to rear
Newer "spool" member, see the slots front to rear at top of the mount pillars?
Newer Mopar "spool" mounts
You can buy these cheap complete as shown at most parts stores, EXCEPT the listing is wrong. They show 318/ 340 / 360 as one part number. You can make them work.