Best Tonearm for Thorens TD-124.

I tried various vintage SME arms, a VPI arm (quite the rarity on a TD124) and then tried my first Reed 3P. Wow!

As mentioned above, you can put just about any arm on a TD124 if you can find a way to mount it without fear of a mismatch. It just boils down to the quality of the arm. 

All of this assumes the TD124 at hand has been optimally updated. 

Reed makes terrific arms, so it is not surprising that it worked well with the TD 124.  Great table + great arm = sonic bliss.  I sort of dislike the notion that a vintage table should be matched to vintage arms; a table as good as the TD 124 deserves a good arm, including really good modern arms.  

Replacement, new rubber mushrooms would probably be the way to go.  My local dealer reconditions and sells a lot of these tables and new mushrooms are one of the basic steps in reconditioning tables.  The person who use to be the dealer's turntable repair/reconditioning/setup person (until recently), most often installs Ortofon and Koetsu cartridges.  He does not like the Black models of Ortofon as much as some lower-priced models because, to his young ears, they sound a bit bright and thinner than the other models.  I haven't heard the comparison myself.

You use the tonearm that works for you, its not a matter of looks table already looks good but you want it to sound right. I use a Audionote Arm3 V2 with Ortofon Quintet Bronze

All of the Ortofon arms became unavailable when Jelco shut down, which strongly indicates Jelco manufactured them.  In any case, they were terrific arms at a reasonable price.  This was one of the preferred brand of arms my dealer liked for both reconditioned TD 124 and Garrard 301 or 401 tables.  Audio Note arms and some Linn arms seem to work well too.