Trading an item is not what the 'Wanted' section is for. You may place an ad in the 'Basses For Sale' section, giving the value of the item to be traded, and specifying 'Trade only; no cash sale'. Any bass can be offered or asked for as a trade, except, of course, Rickenbacker basses, as BC cannot guarantee the authenticity of such instruments. Trading a 35" scale for a 34", for instance, is perfectly permissible, provided that the valuation of the bass is correct.
Hope this helps.