Originally Posted by firstname.lastname@example.org
The one marked at 500 is for a reverse rotation 351w.
The $500 and $65 distributor have the exact same part number.
On the listing for the $65 part, there is this:
Questions and answers about this item
Q: Is the for a standard rotation (same as a car) or reverse rotation? Thank you in advance for you help.
A: These are reverse rotation, for a specific Ford Marine Engine. Thank You
EDIT: Just pulled the trigger on that $65.13 distributor linked above. It seems like a great deal on a new dist. The caps can be found on Amazon/eBay for $20 and Pertronix seems to think that the plate should be interchangeable between the 1581 and 1582 (if you are switching between screw-down and clip-down distributors).