Allright, I've got 2 '328s breadboarded as minimal hardware setups.
Bootloaded both with Uno optiboot, get 3 quick flashes on reset, looking good.
I need to change the CKSEL fuses on one of them to 0000 so I supply it with an external clock (which I will provide from the other '328).
Was gonna do it with AVR ISP MKii, but AVR Studio 5 doesn't seem to recognize it as being plugged in, I am guessing as a result of changing from the AVR Studio default Jungo driver, to the Arduino provided driver for the MKii.
Is there a way to use avrdude or something to change the CKSEL fuses?
Off to bed now, will try any suggestions after work tomorrow.
Thanks!