The technics sl-120 came with an SME tonearm. The armboard on this table will fit on the SL1200.
Rega also makes an armboard to accept their tonearms for the for the SL1200.
If you can find a SME tonearm for cheap I made a jig to whip out some armboards pretty easy out of rosewood I can hook you up with.
I have read of some that have changed the tonearm on this table with the Rega and SME but they have said that it wasn't justified since the SL1200 is already a great tonearn especially with the KAB fluid damper added to it.
http://www.kabusa.com/frameset.htm?/
Let me know if you find a differant tonearm that you would like to try other than the ones I have mentioned. I can make the same armboard without the sme cutout (blank)