Problems Building 5.0 on Solaris

I, foolishly, tried expanding the UNIX archive and typing ./install.csh. I get the following error message:

============================================
Error: Can't find a usable init.tcl in the following directories:
/usr/tcltk/lib/itcl/tcl7.5 /ENGdata/dept9210/amp28609/tars/CD_OpenCASCADE-50/unix/tcl/sun/lib/tcl7.5
This probably means that Tcl wasn't installed properly.

while executing
"error $msg"
(procedure "init" line 29)
invoked from within
"init"
============================================

The message is correct. That file does not exist.
In general, it looks like the sun version of tcl in the archive is incomplete. Unfortunately, I can't download version 7.5 from somewhere to get the files and the installation requires it.

Any help?

Thanks,
Author