Large-scale Fortran development under xenix

[Mason]

Does anyone out there have any experience they could share developing
and/or porting large scale FORTRAN applications to run under Xenix ?

We are software developers with extensive FORTRAN applications running
under SUN-OS and VAX-VMS.  The largest single executable module is 
300,000 lines (oh god!) of FORTRAN (1500 subroutines, averaging 200 lines
each).  

Are software tools (compilers, linkers, debuggers, whips and chains) 
available in the Xenix environment capable of handling programs this
large ?

Which (is there even a choice ?) FORTRAN compiler would be the most
appropriate ?

Any e-mailed comments or suggestions would be appreciated.  A posting
of digested responses would be made to comp.lang.fortran and to  
comp.unix.xenix

Thanks for the help...

Regards,

Stephen Comfort-Mason
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