Not only an extension. As I just put one in my '89 420 SEL, I used a 10 mm allen socket. And a swivel. And a BIG 1/2 inch drive breaker bar. These bolts are self-tightening, seems like. They were just out two years ago for another reason and I know I didn't tighten them that much.

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Gregga
'89 420 SEL "Moby Dick"
'30 Ford Coupe
'31 Ford Slant Windshield Town Sedan
'33 Ford Pickup
'34 Ford Pickup
'01 Honda Passport