I used the fiberglass inner bumper from a parts car. I removed the cover and cut it down so it would be easier to carry all the way out to AZ in the car. The bumper mounts attach to the frame with 3 nuts on each side and attach to the bumper with 4 captured bolts on each side. The tow bar brackets attach to the bumper with one hardened bolt on each side with a type of nut that will not loosen on it's own. As I attached the bumper mounts I wondered if the shock absorber part of the mount would pull out or move at all. That did not seem to be an issue.

If you don't have an extra bumper lying around, you could just remove the cover from the car's bumper and mount the tow bar brackets to it. After the cover was replaced, there would be no evidence of the 2 small holes in the inner bumper. On a 20 to 30 year old bumper you may find that many of the cover's fasteners are rusted on pretty tight. But if you can get them off, it would work.

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Greg
2012 S350 BlueTEC 4Matic
2007 ML 320 CDI
2007 Leisure Travel Serenity
2006 Sprinter 432k
2005 E320 CDI
1998 SLK230 (teal)
1998 SLK230 (silver)
1996 E300D 99k, 30k on WVO
Previous:
1983 240D, on WVO
1982 300D, on WVO
1983 300CD, on WVO
1986 300SDL 237k, 25k on WVO (Deerslayer)
1991 350SDL 249k, 56k on WVO - Retired to a car spa in Phoenix
1983 380 SEC w/603 diesel, 8k on WVO
1996 E300D 351k, 177k on WVO