SME lV arm upgrades?

I wouldn't touch the internal wiring. SME uses (and ONLY in this arm) a special ribbon conductor, similar to that used in Magnan cables and ICs. In fact, Magnan was their original supplier. This conductor is perfect fot MC cartridges, and also offers the least bearing resistance of all.

The one upgrade I would recommend, would be the addition of the optional damping trough, if it doesn't already have it.

From the SME website:

ACCESSORIES - Pick-up arms
FLUID DAMPER KITS
To damp arm motion: Part no. FDIV

For use with Series 300 and Series IV arms. Provides lateral damping only. Also provides for the fine adjustment of vertical tracking angle, a feature standard on the Series V arm. Complete with damping fluid in a syringe and instruction book. Go to:

http://www.sme.ltd.uk/html/spaccess.html

You can buy them directly from SME, or Sumiko in San Francisco. (Factory is cheaper for parts I've found)

You can email Elaine Wratten SME Sales for prices:
sales@sme.ltd.uk

As for whether your arm has one, it would be wrapped around the main pivot post on the inside (platter side) of the post.

For phono cables used, search either "phono cable" or "tonearm cable" here on Agon. I also use a Purist Venustas like Jfrech, and think it's most amazing!