Geoff:
I had 34 ICH carbs on one of my Arnolt Bristols. I can't find a record of the
size of the venturis so the jet sizes that I ran doesn't mean much. However
they were 140 Main, 240 AC & 60 Idle. They worked well for racing, but I can't
vouch for them for street use.

I looked at a chart on:

www.webernorthamerica.com/34_ICH_weber_carb.html -

and saw that it listed 29mm venturis with a range of 130 to 165 Mains
depending on whether the Aux. venturi was 4.5 or 3.5. I suggest that you take a look
there.
Bill