Okay, let me clarify; the u32 module doesn't come with the Linux kernel source.
It's provided by NetFilter, specifically iptables. Version 1.3.4 was released on November 3rd, 2005 (quite old).
Get the source for iptables, either from the repo for your Linux distribution channel, or directly from the NetFilter guys. Then compile a version that meets your needs.
luser@lhost$ find ./iptables-1.3.4 -name "*32*" -type f
luser@lhost$ head ./iptables-1.3.4/extensions/libipt_u32.c
/* Shared library add-on to iptables to add u32 matching,
* generalized matching on values found at packet offsets
* Detailed doc is in the kernel module source
* (C) 2002 by Don Cohen <firstname.lastname@example.org>
* Released under the terms of GNU GPL v2
Read their "INSTALL" file. It tells you how to build iptables outside of the kernel tree (this way you won't clobber your existing install).
3) If you want to specify alternate directories for installation
(instead of /usr/local/ bin lib man), do this:
% make BINDIR=/usr/bin LIBDIR=/usr/lib MANDIR=/usr/man
# make BINDIR=/usr/bin LIBDIR=/usr/lib MANDIR=/usr/man install