Aftermarket carb for 170?

There are Weber adapters, but often the hole for the single barrel is the bottleneck. The Super Six intake manifolds are often a good upgrade for someone who wants a bit more airflow without going crazy; they are set up for BBD carburetors but you can adapt others.

Another option - there's an Offenhauser manifold that lets you run a pair of 1-bbls if you want an exotic-looking but reasonably practical setup.