dash lamp sockets

I got my 74 dart out on the road for my first run today, she runs great but I did find a few lighting issues. it seems that someone in the past had no clue how the lamps in the dash were supposed to be replaced. the sockets that twist into the back of the dash are all broken. I was able to find 3, one for the spedo, and the brake and oil pressure lamps, all 3 had one tab broken off the socket and thus wont lock in place. First question is does any one know if any of the major parts shops stock these? second question is how many lamps are there for the lighting? due to the position I was in when I held the socket in place I couldn't really tell but it did seem to light up the spedo and at least the fuel gauge, is there more than one or does that one do it all?

Thanks