That P/N comes up on PeachParts here, Genuine MB special order for $136.00. That being said, the mount does not come up on a general search for the 108 4.5, so if the dealer comes back with that part number you should be good.

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Current:
2021 Charger Scat Pack Widebody "Sinabee"
2018 Durango R/T

Previous:
1972 280SE 4.5
2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi"
1999 Chrysler 300M - RIP @ 221k