If you don't keep the boat in the water, I'm not sure you'll need them. Sterndrives need them because aluminum is a reactive metal and is depleted faster but bronze is more "noble".
This is a quote from http://gulffishing.com/tips_anode.html
"The hull material of a boat determines, in part, which anode material to use. A fiberglass boat having an inboard engine with bronze and stainless metal parts needs less protection than an aluminum hull or a boat with an aluminum sterndrive.
Aluminum alloy is the only anode material that is safe for use in all types of water and accepted by the major sterndrive manufacturers as the best material to use. It is lighter and protects better than zinc and is not so active that it becomes dangerous like magnesium. Aluminum alloy is also environmentally friendly, unlike zinc, which is considered a pollutant."
If you drill holes in your tracking fins and install anodes, they'll stop being tracking fins.