The best treatment for class V lesion on a tooth along with extensive class II caries is:
With class V lesion and extensive class II cavity in the same tooth  the  remaining  enamel  surface  with  the  supported healthy dentin will be much less hence  in such situation full crown restoration will be long lasting.
Restoration of class II followed by class V
Cast gold restoration
A full  crown restoration
Restoration of class V followed by class II