DD question

I don't know if this list is still active, but here goes.

I powered up a 4.0d system that has been asleep for quite a while
and while booting, it crashed owing to what appears to be disk failure.

I subsequently put in another drive and reinstalled 4.0d on that and attempted
to get the data off the bad drive  (both / and /usr, a and g partitions)  couldn't
mount them, but succeded in using dd to get a number of records off them.  The bad
drive was rz1  so I copied to the new /usr using

dd if=/dev/rz1a of=/usr/rz1a  and similarly for the g partition

How do recreate (if possible)  the file structure from these files?

Tom