In mine (1978), there was a wire conduit in the mast, although the previous owners had not used it (the banging of the wires inside the mast used to drive me crazy at anchor!). When we rebuilt the mast a year ago, that was on of the things I made sure to fix.
If you're doing this with the mast down, here's a real easy neat trick for getting a messenger line thru that long conduit.
Get a long ball of twine. Tie a small "flag" of paper to the end. Hook a shop-vac to one end of the conduit to provide suction, and feed the twine into the other end. It'll suck it all the way through, neat as can be! Then use the twine to pull a stouter 1/4" line through to use for the actual pulling.
When I pulled the wires, I put in an extra pair for future additions, and I also included a piece of twine to use as a messenger again in the future if and when its needed.