The engine was made on 9 November 1983, so the mower was probably made fairly early in 1984. The plant where the engine was made (Plant 12) has long since been closed - at this point I can't even tell you where it was located.

Here is the Illustrated Parts List:
http://bsintek.basco.com/BriggsDocumentDisplay/Z6nlxBVJ1DajI.pdf

Here is the Operator's Manual:
http://bsintek.basco.com/BriggsDocumentDisplay/msozHP-K_ny7tH217FzoPu.pdf

There is a fairly full set of Briggs technical manuals available for download from the Outdoorking manuals section (subscription required), here:
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=20019#Post20019:

The one that best covers your model is "Briggs and Stratton Service and Repair Instructions 1984", though the later side-valve manual, Part Number 27062, "Single Cylinder L Head Technical Manual", is just about as suitable - the main differences are it also covers post-1984 models, and has less detail on early engines. If you intend to overhaul your engine, in my opinion it is best to do the job with immediate access to the manual.

We'll be happy to help you as you go: just post to this thread.