Problem with old code while installing Dock6 - fortran

Question

I'm trying to install Dock6 (version 6.9) on Fedora 35, I got the license from the website, opened the tarball and followed the manual instructions.
As per the instructions I've run the command ./configure gnu to create a config.h file which uses the gfortran compiler, installed the latest version of gfortran and run Make all.
The problem seems to be that the source code was written with g77 in mind and I get a lot of warnings and 2 errors saying:
Warning: Fortran 2018 deleted feature: DO termination statement which is not END DO or CONTINUE with label 20 at (1)
cdiag.f:388:72:
388 | 50 CALL ME08B (A(K,K),Q(K),A(I,K),N-K+1,IA*2)
| 1
**Error: Type mismatch in argument ‘a’ at (1); passed COMPLEX(4) to REAL(4)**
cdiag.f:15:72:
15 | CALL EC08C(W,W(N+1),VALUE,VEC,N,IV,W(2*N+1))
| 1
**Error: Type mismatch in argument ‘vec’ at (1); passed COMPLEX(4) to REAL(4)**
make[2]: *** [../../../install/rules.h:44: cdiag.o] Errore 1
make[2]: uscita dalla directory «/home/francesco/docking/dock6/src/mopac6/src»
make[1]: *** [Makefile:21: utils] Errore 2
make[1]: uscita dalla directory «/home/francesco/docking/dock6/src»
make: *** [Makefile:14: install] Errore 2
so i read in the config.h file that it was also possible to compile with g95 and g77.
If I compile with g95, which I managed to install, I get this error:
**f951: error: unrecognized command line option "-fno-automatic"**
make[2]: *** [../../install/rules.h:44: showbox.o] Errore 1
make[2]: uscita dalla directory «/home/francesco/docking/dock6/src/accessories»
make[1]: *** [Makefile:16: utils] Errore 2
make[1]: uscita dalla directory «/home/francesco/docking/dock6/src»
make: *** [Makefile:14: install] Errore 2
regarding g77, I just cannot find a way to install it, I managed to find a .deb package, converted it to RPM using alien command, but it doesn't complete the installation saying it conflicts with something in the system.