Dash lights not working

[Bullett]

I am putting a new Skool dash guage assem. In my 62' c10. I am planning to use the original dash light circuits to feed the lights on my new gauges, problem is, none of the light bulbs work except for 2 of them. These 2 lights are the only 2 in the cluster that have the black plastic sockets. The rest are all metal type bulb sockets. The 2plastic ones that work go to a couple idiot lights in the factory cluster, don't remember which ones. These 2 bulbs stay lighted up 24/7, wether the light switch is on or not. They eventually drain the battery. O.k., back to my questions, why do these 2particular bulbs have a plastic socket compared to all the rest having steel sockets? What would be a best guess as to why the dash lights won't light up? The fuse in the fuse box looks good. All the rest of the lights on the switch work fine (headlights, tail lights, parking lights). Could the switch be bad even though the rest of the lights, except dash lights, are working? The wiring under the dash has certainly been whacked and hacked over the last 51 years but I didn't see anything real obvious. Any suggestions? Thanks