its not all that bad and its better to change them now before one goes. last thing you want is to snap some rocker arms.
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pull the radiator and it gives you plenty of room
unbolt the crank pully and remove the dust cover your good to go.
the biggest problem is getting your marks to line up.
just besure to make a refferance mark on the ip pully when everything eles is lined up so it goes back the way it came off
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this was before pulling motor

owned a few .. current 86 rustbucket 2.5td . manual hubs