vncserver is a wrapper for Xvnc, and the Xvnc man page says this in the options section:
Specifies the port on which the mini-HTTP server runs. Default is 5800 plus the display number.
So, I assume that you could run vncserver with the same option, and give it 80.
Edit: as a matter of fact, I know you can. From the vncserver man page
vncserver - a wrapper to launch an X server for VNC.
vncserver [:display] [-geometry widthxheight] [-depth depth] [-pixelformat rgbNNN|bgrNNN] [-name desktop-name] [Xvnc-options...]
So yes, `vncserver :0 -httpPort 80` - plus whatever other options you use - ought to do the trick.