To have two servers with the same server name and same tree name on the
same cabling IF their IP assignments are different? Obviously there are
DNS issues but would NDS have a problem. What I want to do is create a
new server with the same name, same tree. Manually rebuild NDS then
copy the files onto the new box via an intermediate server that I will
move between the two networks by changing it's IP. Once all looks good
I will down the old box, change the IP of the new one and go from there.

I'd use the migration utility but the originating 5.1 server is at SP0
and does not meet migration tool requirements and I don't want to fuss
with it at all since it's got 4 years of uptime.

It's a small network so reconstructing NDS is not a big issue and there
are some design issues that can be addressed.