Be careful of halogen bulbs, they can get too hot and burn/melt your lenses as well as draw more electicity/ amperage. Recommend instead LED light bulbs which give more intense light/ brightness and draw less amps than normal bulbs. I have not seen the two bulb system you describe but the LED bulbs can be purchased from Randall Thomas who is an offroad builder but also a SPF owner and seller of Cobra related parts ...try his website at ( hope this is right):
www.performanceunlimited.com and search for the Cobra items. I added the LED bulbs to my SPF which were also dimmer than desired when stock bulbs were used and now have brilliant lighting. Bill Wells