Well, here's your 12V for the radio fixed........
http://www.ebay.com.au/itm/Classic-car-6V-to-12V-voltage-converter-power-power-/350436684000
http://www.ebay.com.au/sch/i.html?_odkw=6V+to+12V&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.X6V+step+up+12V&_nkw=6V+step+up+12V&_sacat=0
I might also add that buying a small 12V "Gopher" battery will drive your average CD/Radio for days on end (just not amps and stuff too), and will recharge overnight easily.
Yes, the lights will be crap, but still OK enough to potter around at nearly 100kph through the city if you want. You can get more than ignition power out of a 6V system to fire up a 100HP motor happily, old 1959 and earlier speed equipment is the coolest thing on the block right now, and original working semaphores on an old car in traffic just about has to be the best thing in our modern world I've seen for decades!