I did a similar fill, but used cheaper black polyurethane roofing caulk (PL1, I recall, $6 for 10 oz tube) from Home Depot (post w/ photo). I just installed them in my 1984 300D (during another job), so won't know for a year or two how well they last, though I have found polyurethane to be very durable in other applications (50 yr warranty). The mounts on there were only ~2 yrs old, but were starting to sag and look pregnant. Probably DEA (India) or branded URO. I forget. Anyway, the rubber is still good, so I will fill those also.

Good you protected your oil cooler hose from that evil pwr steering pump V-belt. My son pulled into the driveway after a 500 mi drive a few years ago, with oil dripping everywhere and the AC belt broken and dragging the ground. The p.s. belt had flipped over so the "teeth" were outward, letting it "chain-saw" a small hole in the oil cooler hose. My guess is the AC belt broke, then tangled in the p.s. belt. There were still >2 qts of oil in the pan. Interrogation suggests it happened just 2 miles from home, since he lost AC and started hearing noises (real lucky). The motor mounts might have been a bit compressed, and the oil cooler hose cocked too much toward the p.s. pump. I had a spare cooler line. I will replace the hose on the old one to get ready of the next pass (good post here on that), though I wrapped the oil cooler hose w/ metal wire to protect it.