Higher stall torque converter with large bolt pattern?

In answer to your question, higher stall converters with the larger bolt pattern are indeed available. It will in all likelihood though have to be custom built. It's not one you're likely to get through Jeg's and the like.
Contact one of the high stall builders and give them all the information about your setup and go from there. Any good converter builder can/will build you anything you require for your application.
I've personally seen 10" high stalls with the large (12") bolt pattern.
Drilling extra holes in your flywheel IMHO weakens the flywheel, and the holes drilled need to exactly centered. With a properly weighted converter, there should be no reason not to use the same flex plate the factory used.
Others may disagree.

I forgot to give you this bit of information. From the factory, the 440 engine with a cast crank used a 12" diameter converter. It has 2 balancing weights welded to the backside(engine side) of the converter. Each weight measures: 1.20" x .75" x .158".