Okay, the possibilities....
Originally, the winch was attached under the step into the cabin. Some old boats have a piece of aluminum or wood added on top of the step for added support to hold the winch. Is the fiberglass cracked where the winch is supposed to be attached? Is that step warped out of normal position? Maybe that's why you have that piece of wood there. The easiest thing to do is go find a similar Mac boat and look at their installation. The 22 and 25 are almost identical with each other. I assume that the 21 is also the same set-up. Send me your e-mail address. I may be taking a vacation motorcycle trip before June to visit a friend near you. If I do go soon, I'd be happy to stop by and inspect what you have. mtnpilotdiver@msn.com