Wood top bows are tacking forms which are embedded in the top frame. In the early Ghias there was a wood bow below the rear plastic window which is attached on the shelf of the car. This was eliminated with the introduction of the rear attachment cable in 1968.
We recommend that you not use cheap plastic top bows, also called "wood replacement bows." They have a tendency to chip and even crack upon being stapled; these "wood replacement bows" do not hold staples well. They are very inferior to the real wood bows.
The full restoration of a Karmann Ghia convertible top (the top itself) begins with the Ghia convertible top frame. Once the top frame is sanded
and lubricated to restore it to proper functioning, the convertible top frame parts must be addressed. The wood top bows will provide, by far, the best staple holding and retention, much superior to the varathane used in Ghia wood replacement bows. In order to keep the top bows functional in top after top, you can treat the wood as you would any exterior wooden product, either with penetrating oils or with exterior paint.