I think the FTN95 library routine CMNAMR has not been ported to 64-bit, or has a different name(?).
In addition, the function gmtime (used in 'C') is not present.
I an running across a few more I'll list here; I'm not sure I have a workaround on these yet. All of these are 'C' routines.
vfprintf vsnprintf fdopen
hypot - This one calculates the hypotenuse of a right-triangle. I can probably provide my own.....