I' am putting lights and turn signals on car, will be adding extera battery for this. Will it be okay to tie both negatives to the chassis, I have another battery for starting and running
Yes,should not hurt a thing.
Unfortunately, nobody manufactures a bulb-socket adapter for pre-1915 side lamps, so you'll have to make one out of wire coat-hangers. I use a brain-box from "Tickin' Through Time" and it has been perfectly reliable for four years, now:
I didn't care for the supplied switch and instead, got a much smaller on-off-on switch from Radio Shack. It's hidden in my Hand-Klaxon mounting bracket.
Lang's sells tail-light housings and brackets that fasten to the saddle arms and look more or less unobtrusive. They'll also work as brake-lights.
Tickin' Through Time also makes a 4-way flasher kit.