Have you seen if Linux can mount your images?
http://wiki.netbsd.org/tutorials/how_to_mount_ffs_partition_under_linux/
OR any of the actual BSD systems for that matter?
It looks like FUSE support for UFS2 exists:
https://www.gutzmann.se/confluence/pages/viewpage.action?pageId=6651931
That would give you the ability to tweak a user-mode program if anything
is different.
And of course you can find historical BSD code at:
http://minnie.tuhs.org/cgi-bin/utree.pl
http://www.tuhs.org/