Ok, looks like I found the magic word. Searching for "p2v" (physical to virtual) turns up a lot more useful stuff than I had managed to find before.

Looks like I can achieve the Linux migration like this:

- create target VM, complete with empty virtual disks
- boot target VM using a Linux boot CD
- boot source machine using a Linux boot CD
- use dd+nc to stream raw partitions from source to target

The remaining challenge will be to get working Redhat 7.1 drivers for the VMWare/VPC "hardware".