Rich,
What I've done to arm my Vanguard Vets was basically use a Terminator Assault Kit, and clip the weapons off at the wrist. I then take a pair of Close Combat weapon arms (like the ones from the Assault Marine kit), and clip off the pistol and chainswords at their wrists, file down the rough edges, and then glue them on the wrist.
It does look a little funny, with a slightly oversized wrist and a thinner arm, but I think it does the trick pretty well.
Here's a couple of pics of what I've done so far: