My Superstar flew great on 34" floats and Enya 45 up front. The LA40 might do the job on a good day but you'll likely need a bigger motor. A 46FX with an 11-6 prop is what powers mine now and it's ideal. VMAR makes a light, 35" ARF float. Since your model is a beater, just glue plywood reinforcements on the outside of the fuselage for the float attachments. A big balsa sub fin makes the Superstar fly better too. Nobody wants my 6 yr old crate either so I lend it out to friends that are between models and don't have anything to fly.

Don't launch your floatplane like this guy!