Hi Keith,
I ended up getting an adaptor plate made up & fitted a 186 carby onto my manifold. The motor is stock bar a set of extractors but it did seem to perform a little on hills on the way to Orange. So I would recommend this mod as a cheap way of helping a stocky breathe a bit easier.
Dean.
I with Pedro on this one, go the twin carb setup, if the car has a stock cam, fit a pair of the 1 and 1/16th venturi's and try it from there. You will probably have to get some smaller jets or fit adjustable main jets to get it running right.
You could go the 1 and 3/16th venturi's but you will be coming close to over carburating you engine. If you then fit a wilder cam, do head work etc you wil be able to do much, much more
Keith