Installing "untrusted" python an a PG 7.4.3 DB

All,
I configured PG 7.4.3 --with-python on a Linux RH 7.3 box that has a
Python 1.5 installation. Then I 'made' it, 'install'ed it, and started
the database without incident. Then, the attempt to install the
"untrusted" version of Pyton in a DB (which the doc says is the only
supported one at this point) yields:

bash-2.04$ createlang plpythonu bazoo
createlang: missing required argument PGLIB directory
(This is the directory where the interpreter for the procedural
language is stored. Traditionally, these are installed in whatever
'lib' directory was specified at configure time.)
bash-2.04$ createlang -L /proj/thriller/pg743/lib/postgresql/plpython.so
plpythonu bazoo
createlang: unsupported language 'plpythonu'
Supported languages are 'plpgsql', 'pltcl', and 'plperl'.
bash-2.04$ ls ../lib/postgresql/plpython.so
../lib/postgresql/plpython.so

As you can see, the plpython shareable is where it should be, but
creatlang doesn't seem to recognize the existence of Python itself. (I
get the same error when I try to install 'plpython).

Python itself runs fine on this machine, so I'm stumped. Any help would
be appreciated.

Sincerely,
Rich Cullingford
rculling(at)sysd(dot)com