Resotre to main drive
 

I have a clone and a safety clone partioned on an external firewire drive.
Everything works great and both are bootable. My original internal drive
is 40G and I added another internal 160G. My question is I would like to
remove the original drive that is the master and replace it with a a larger
drive. If the new drive is set to master would I be able to clone back to
that drive from the external clone or do a restore from the external clone?

As a general rule, if the drive would be bootable with a straight OS installed to it, it should be bootable when SuperDuper! copies an OS to it. So, if the externals are all bootable (as you indicated they are), you should be able to replace the drive and clone back without any significant issues.

Thanks for the info. The reason being I would like to clone back to the new drive is that my machine is almost 4 years old and I started with OS 10.0
and really do not want to go through all the upgrades to get me back to 10.3.8. Would I do a clone or a restore from the clone or would it not matter? Thanks for your help.

I'm not sure what the difference is -- could you explain a bit more what the two options you're thinking of are?

I don't think I worded my last replay correctly. I just want to make sure if I add the new drive as a master would I have to have an OS installed on it
or could I just clone from the external drive? I hope I am phrasing this correctly.

You should just be able to clone from the external drive after booting from it.