What modifications do I need to buy to have the stage 3 cam working well?

Ideally, you would require the following items:

Valve springs 130# http://www.maceengineering.com.au/epages/shop.sf/en_AU/?

Valve spring Retainers: http://www.maceengineering.com.au/epages/shop.sf/en_AU/ObjectPath=/Shops/mace/Products/SPG601/SubProducts/SPG601 

Viton Vale Stem Seals: http://www.maceengineering.com.au/epages/shop.sf/en_AU/?ObjectPath=/Shops/mace/Products/SPG604 

Double row timing chain set: http://www.maceengineering.com.au/epages/shop.sf/en_AU/?ObjectPath=/Shops/mace/Products/SPG605 

You would also require a Custom tune: http://www.maceengineering.com.au/epages/shop.sf/en_AU/?ObjectPath=/Shops/mace/Products/RLM601 You would also require a Custom tune.