Stribo,
Mine's a supersport, forgot to mention that.
If you want big dollars, say around $4000.
The bike will have to be MINT.
Look for original exhaust system, the original headers on a 400/4 are said to be the the most beautifully constructed headers ever installed on a jap bike as original equipment.
Check for tool kit, user manual, original seat, handlebars, indicators, orinal paint scheme, little details like the fuel tank stickers add a lot a value at the top end of the collectors market.
But what ever you do, don't keep it under covers. Ride the bloody thing

Check out this mint example!!!