I want to connect an iMac G3 running Mac OS 8.6 to my Ethernet network. The easiest way for me to do this is to change the iMac's MAC address.
Is it possible to change the MAC address and, if so, how should I do it?
There's a piece of abandonware called "Relocated" that was written by Robert Sixkiller & Adriaan Mol in the early 2000s. It will allow you to change (spoof) your MAC address in MacOS 8 and 9. You can find a copy here.