any simple tool to extract files from an UFS image ?

Hi,
I am doing some work recently on small FreeBSD images (picobsd and friends),
and I need to run on a linux machine some script to customize
both the UFS and the ISO image.

Because the customization is just writing some text into a file,
my approach is to put in the UFS image a file with a recognizable
start and end markers, and then dd into the image the stuff I need.

I was wondering if i could avoid shipping both images, and instead
use some trick to extract the tree from the UFS image and then
use mkisofs on the linux side to build the ISO.

I know that bsdtar can read ISO images, but I don't think it does
the same on UFS. Yet, if the boot2 code is able to squeeze the
required pieces on 8k or so, maybe there is some simple (and portable)
tool that can do the file extraction job ?

	cheers
	luigi