Sonic TDM always fascinated me but like you, we used RevRdist for patching and cleaning Macs. MacPrefect kept them very clean anyway. IIRC, Sheffield University were quoted as one of the UK adopters of Sonic TDM.Wow. This question triggered some long forgotten memories! I used to work in a student computer lab where we wanted to do just this. We had a mix of LCIII's and (new) PowerMac 6100's. We did in fact get this to work using "The Diskless Mac" from Sonic Systems - which was essentially a boot ROM that replaced the onboard ROM on a PDS or NuBUS (was the 6100 NuBus - I cant remember) ethernet card.
Google "The Diskless Mac" with "Sonic Systems" and you'll see how it works. We did this with System 7, but I have to tell you that we abandoned the idea not too far into it - the problem was when you had 40 machines all reboot at the same time - veeeeeeeery slow. A few machines at a time was fine however, so not likely to be a problem if you can find any of this kit
Sonic NICs were always well made and used the same chipset as Apple. They had a socketed EPROM which was swapped out for the TDM version, I believe. Did it require a NetWare server to provide RPL?