[Mark Yacavone]

The 8" converters in Stockers, usually start out with a factory designed stator profile. Those designs most often multiply more torque due to their larger diameter, among other things .
The 7 inchers most always use a fabricated stator, which fulfills it's function to a certain extent but are usually used in a super high RPM range.
Given the lower torque curve, (dual plane manifold, small ports, valves ) of a 283 Stocker,
I would tend to favor the 8" style. That's not to say that 7 inchers haven't been used successfully in Stockers.
Sorry for not giving a definitive answer here, but I think it may depend on who you're working with.
I don't want to leave anyone else out but I think I would want to work with A-1 on a 7" in your application.