Comparing drivers for Mk3 vs Mk2 on the Japan site many were identical, only a few HotKey different, plus something called Extended Thermal Model (ETM) new to the Mk3. So I ran the Recovery DVD on a Mk3 unit, then after it loaded but before rebooting I pulled the hard drive and moved it to a Mk2, then let it boot and initialize in the Mk2. Everything seems to work great. Checking the Device Manager, there is a System device for a thermal sensor that would not start. I opened the C: > Util > Driver folder and clicked on Install for the ETM and what do you know it Uninstalled the ETM software. No more thermal sensor driver problem. I guess that sensor had something to do with Core Duo in Mk3, where a Mk2 only has Core Solo.
I've copied the modified Mk3 load and installed it on several Mk2 units, they all run great.