Courtesy Light ??

[3 on the tree]

My 70 Blazer lists a courtesy light, code 4U29AA. All I can find is a single socket under the dash on the driver's side. Was a dome light a seperate option, cause there is no evidence of a dome or side light anywhere in the cab. I also noticed what looks like provisions for shoulder harnesses built into the dbl wall top. When did Chevy start production of shoulder harnesses?

 

[85mudblazin]

I know the newer blazers (90's) have the shoulder belt that mounts to the top.