does a 1985 dodge W150 truck have a "check engine light"?

Answer 1

It might, but perhaps not. This is a break-over year/model.
Look under the hood, and find the emissions label. If it is Federally certified, probably not, but if it is California certified, it could be equipped with a light. Depends on the weight class.
An additional thought; look to see if there is an oxygen sensor somewhere in the exhaust manifold, or in the pipe between the manifold and the muffler. If ther isn't one, there probably isn't a computer, and no need for the light.