Chosen Solution

My 1985 300D front rubber trim is loosening from it’s bumper. I tried to get the clips back into place and slide the impact strip into place. Unfortunately, it will not remain snug. Advice and directions to fix would be most appreciated. Thanks in advance.

Sounds like your not getting the clip far enough onto the rubber backing . A near impossible task on dry rubber. If you were to spray the rubber with a spray lubricant like liquid wrench or wd40 you’ll find you can push the clip on further and then when you assemble your fit will be tighter. Hope this helps