Front End Rebuild - my first rodeo
Original Chrysler idler arm had a rubber boot.
Chrysler part number 3402846 which supersedes to 4014089 both came with the rubber seal.
You can see examples of both numbers on eBay.
Search: 3402846 Mopar and 4014089 Mopar.
Ignore what the sellers say about what 4014089 fits.
They don't know the 4014089 is a superseded number that also fits 73-76 Abodies.
Unfortunately Moog has been using those foam seals for decades.