Two more preprocessors of that era include SFTRAN and S-Fortran.
In one of my favorite Fortran books, FORTRAN Tools for VAX/VMS and MS-DOS, the authors write a full Fortran preprocessor (in Fortran of course) just to add some nicer loops and if-clauses, and to bypass the six-character limit on identifiers using a slick hash table implementation. Only 4 years after they had gone through the trouble, the Fortran 90 standard raised the limit to 31 characters.