Best SME arm for TD-124?

Albert is correct; I would just add that it also depends on your choice of cartridges. The older SMEs work well with MM, not so well with most MCs. If you want to use MMs you might consider a Type 3 arm, which was better than the 3009 type 2 and is often available at a favorable price. Not period authentic but should be a good match. Like Albert I have been around a while and use to use the Ortofon RS 212, it should still work if you want to use MCs.

Salmonsc, I was about to post a comment similar to Stanwal's, it depends on your choice of cartridges. I believe that relationship is far more important than any arm/table matching.

Mass, rigidity, geometry, and materials in the arm all come to play when matching a cartridge. If you can first identify the character of sound you are looking for and then find a few cartridges that satisfy that sound, then you can select a compatible arm. So long as that arm is correctly positioned and securely mounted, it should work fine with your TD-124.

Thanks for the input folks. At least initially, I will be using a Shure V15 III - & have narrowed my choices to the SME 3009, either the Series II improved or the Series III.

I agree with all previous comments and add that a properly restored TD 124 can do justice to an SME V and SME IV. For grins, I put a Graham Phantom and Shure V on my TD 124. It sounds excellent, as does a SME IV and Benz LP on that same TD 124. A properly restored TD 124 is a must to get great results out of a nice arm / cartridge combo. If nostalgia matters, the 3009 II looks and sounds good too.

If your base can accommodate a 12" arm, the Schick 12" works very well on the Thorens.