Restoring a disk image with dd

I made an image of a complete disk with :

$ sudo dd if=/dev/sdc | gzip -c > my_image.dd.gz

When I restore it with :

$ gunzip -c my_image.dd.gz | sudo dd of=/dev/sdc

I get errors when I type :

$ sudo sfdisk -l

Output of sfdisk :

Disque /dev/sdc : 1022 cylindres, 247 têtes, 62 secteurs/piste
Unités= cylindres de 7840768 octets, blocs de 1024 octets, décompte à partir de 0

   Périph Amor Début     Fin   #cyls    #blocs    Id  Système
/dev/sdc1   *      0+    637-    638-   4881408   83  Linux
                début : (c,h,s) attendu (0,33,3) trouvé (0,32,33)
                fin : (c,h,s) attendu (637,158,50) trouvé (607,212,53)
/dev/sdc2        637+    892-    256-   1952768   83  Linux
                début : (c,h,s) attendu (637,158,51) trouvé (607,212,54)
                fin : (c,h,s) attendu (892,166,20) trouvé (850,240,30)
/dev/sdc3        892+   1022-    130-    995328   82  partition d'échange Linux / Solaris
                début : (c,h,s) attendu (892,166,21) trouvé (850,240,31)
                fin : (c,h,s) attendu (1022,163,42) trouvé (974,218,12)
/dev/sdc4          0       -       0          0    0  Vide

For the non-French speakers : début = beginning, fin = end, attendu = expected, trouvé=found, vide=empty, amor(çable)=bootable

I think it's because I forgot to use the dd option conv=noerror,notrunc,sync when I created the image and the data alignment in the file systems got messed up.

I don't have the original disk at hand. How can I restore the image to a new disk ?

OK, I fixed it. The 2 disks have the same size, but different numbers of sectors per track. As I have access to the source machine over the internet, I could save the partition table :

$ sudo sfdisk -d /dev/sda > smps02_partitions

Once transferred to my local PC, I applied the partition table to the new disk :

$ sudo sfdisk --force /dev/sdc < smps02_partitions

Finally, I could boot into the system.