Chiltons if overcomplicating that. As long as you're doing nothing to move the crank, just mark the block and base of the distributor with a Sharpie and mark where the rotor is situated in relation to the body of the distributor. When you put it back in, just make sure the marks line up. Set your timing afterward.
Oh, stuff a towel in the distributor hole to keep dirt and coolant out of the block.
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351W 89 Mustang GT Convertible