A little more time for a better answer
That is a very poor design.
A better design would be to replace the whole idea with a modern one.
Remove the car and the stainless steel wire (Discard).
Verify that there is a simple or cascading outhaul purchase inside the boom, attach the purchase to a piece of 1/8" Dyneema long enough to replace the SS outhaul wire that you are replacing. Splice the dynema to the clew thimble. This is one of the easiest splices to do by the way.
Remove the sail from the boom track, and run it loose footed, use a velcro band to attach the mainsail clew to the boom. Or if you are on a budget or wish to seem really race oriented, tie up a soft shackle for it yourself which goes around the entire boom and threw the sail clew keeping the clew close to the boom. This is an excellent use for Dyneema both for strength and slipperiness.
The sail will move more freely, and your control over sail shape will make the outhaul a useful sail trim control, instead of a set and forget non functional mess that it is on a lot of 70's boats. It will be stronger, less prone to chafe, easily inspected, cheaper, and easier to use.... Hmmm that doesn't sound very nautical does it? Something better that is cheaper than the more expensive version?
Total cost for the mod done this way if you learn to splice the dyneema (really the easiest and most fun to make splice there is!), and make a button knot for the soft Shackle? Less than $40.00 assuming that you can use your current outhaul tackle that is in the boom.
Guy