I cannot help you with the filler plate question as I run the "96" series walker machines. You can run auxiliary lights on any machine if you run a power wire direct from the battery to a relay, using a separate switch. Make sure you use a circuit breaker at the battery connection, NOT AT THE lIGHTS. Hope this helps you.
Another enhancement is now available from loewen, an adjustable louvered precleaner. The precleaner on the STS has solid louvers, which won't move. They also make an airfoil chaffer, and the plastic clean out spout for the vertical unloading auger.