"how do I install them? Leveraging with a screwdriver?"

To help them become more pliable, I drop the rings into some hot tapwater for @ 5 minutes. Then push up on the muffler til the hangers on the mufflers are almost touching the hangers on the chassis then just muscle the rings into place. Usually a punch or a toothless plier will work if you can't stretch 'em on by hand.
I always replace all of them at the same time.

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Bama1


2008 SLK 280, Firemist Red - "Hurricane"
2001 F150 Lariat 4x4, Black on Black - "Badboy"
1982 240D 4 speed survivor -"Pearl" - Donated to Vietnam Veterans
1962 Oldsmobile Dynamic 88 -"Gertrude"

1954 model original owner - ~2.5M
Gray softtop/solid exterior/modified chassis