Read a SAS data file into R based on a SAS script (NHANES III)

I am attempting to read NHANES III, a publicly available epidemiological dataset.
It is not clear how to do this but they do provide a data file and a SAS file:
https://wwwn.cdc.gov/nchs/data/nhanes3/1a/adult.dat,
https://wwwn.cdc.gov/nchs/data/nhanes3/1a/adult.sas.
The data file does not seem to be a conventional SAS export format. and the SAS file seems to describe its format with LENGTH, FORMAT, INPUT and LABEL headers.
Any idea how to read this into a friendly format?

A well-known dataset like this almost always has an R package to handle conversions. In this case nhanesA should fit the bill.

However, the nhanesA package seems to only download XPT files of the database after 1999.

NHANES practice is to release data as SAS transport files, which can be read directly by a number of applications. FAQ.

The purpose of nhanesA is to convert those XPT files into R tables.