Most of Wallyworld's $15 driving lights are 55w, tho small they are quite hungry. Still a driving light (or fog) would make an excellent headlight. They also have "trim" lights, those small ones on running boards etc. - available in both red and yellow, they would make great brake light/turn signals. Best yet those are available in LED for about $5 each.
At VIP auto (a major chain auto parts store) I saw the same style driving/fog lights in LED - I'd check those out for max batt life, prolly not as bright as the 55w halogens, I suppose you could have one of each, run the LED for normal conditions and to save power, saving the halogen for "high beam" use.
Lookin good man!
Just wanted to mention, at "Home Depot" or it's equivalent they have 12v DC halogen spot or flood bulbs w/focused housing, meant as a replacement bulb for home lighting - make a housing/mount for the connectors and the "spot" would make a great
distance headlight - or one of each, flood for area light/spot for distance. They consume a touch less power and at $3.59 - it may be worth it to make a mount
BEAM SPREAD-10 DEGREES