In grad school, I revived some FORTRAN66 code for aircraft sizing. (You can probably download an equivalent model from Dan Raymer's website as an Excel workbook.) This was not its first revival, according to the comments in the code. That was when it was transferred from paper tape and adapted to run on VAX/VMS. Nor was this its second revival. That was when my advisor had made the VAX/VMS version work on SunOS when he was in grad school. No, this was its third revival, wherein I took the SunOS version and made it run on modern Linux. I'm sure a seasoned veteran would have known about the magic compiler flags that made it not produce garbage, but it took me several days of trial and error, and reading the gfortran man page. Along the way, I got to learn about Hollerith constants! Some day, I'm sure another generation of grad students will renew the great tradition, adding their own comments below mine.
You would have been much better off nowadays, because the legacy vendor-specific features have mostly landed into gfortran (recently) behind flags. This is specifically to aid porting off old compilers onto GCC/Clang.
