With some time, between @MidnightSwinger and myself there should be some info for these dual setups. I have the same Offy 2x1 that was modified for a 2x2. I'll be trying a pair of 32/36 Webers first, if that's not enough pizazz I have a set of 38/38's to try. Those should be enough carb for a moderate slant.
A funny aside, this photo is not my car, but it's from the member where I got the carbs and intake. It turns out the rest of this is now the engine going in MS's Dart. It's a small world sometimes!