I've never
had a problem with using a 4.1.3 binary on earlier 4.1.X. Looking
at my gcc distribution. I've put a distribution at
http://setiathome.ssl.berkeley.edu/~korpela/gcc_sunos_4_1.tar.gz
It extracts to a subdirectory (gnu). The executable directory is
gnu/H-sparc-sun-sunos4.1/bin
The only issue is with some dynamically linked libraries (linked
against shared libraries that don't exist....
Some symlinks usually fix that.
I'm surprised that the directories are hard coded in the executable. Usually
LD_LIBRARY_PATH is searched, so you can add library directories to that.
Eric