Thanks for the advice, gutmensch -
could you check config.log after running configure for occurances of special version checks?
Nope, doesn't seem to be any version checking.
Tried to add -I/usr/local/include/ImageMagick to CPPFLAGS? PKG_CONFIG_PATH is correctly set to at least /usr/local/lib/pkgconfig:/usr/lib/pkgconfig?
I'll try a rebuild using -I and see what happens.
The weird part is that it all just compiles/builds fine ... it's the final binary that demands v4 libs. They're not even on my system during the build, so I don't know why the whole build process accepts v5 but the binary doesn't. I'll keep working at it.
[EDIT:] +1 to gutmensch - adding the include directory to CPPFLAGS solved this. Thank you much!