The spares I found are 66mhz got by my dad many years back to up his 466/socket370 celery box it seems.
I have got one spare IBM Xseries that I got in with a job lot, I have yet to lay eyes on it since,
but it was mobo/cpu/raid/case backup for the others looking at my notes,
if it can work for you and
cant make a pair with the single in my supermicro its yours.
As for the speed thing there should be no problem underclocking them the coppermines(T ?) were all 100/133mhz were they not???
I underclock my Athlon XP box all the time with speedfan when its not doing any real load.
Sorry about the time delay our phone lines got dug up/something and I have just got back on with a sub 1 MB connection

I hope they are going to get it back all the way ...how did we ever manage with 300/75 ?