Got a little firsthand experience with this one! The Caddy distributor has a different housing height than a Chevy, and I think it's a left-hand rotation, also. The shaft length is the same, but it has a different dimension from the block to the top of the distributor. You'll need a Cad distributor, probably from a 500 CID engine. If one isn't available from a wrecking yard, NAPA, or some other professional-level parts store probably has rebuilt units available by special order.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
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