What converter stall should I use?

Same old answer.
Ask the converter manufacturers, not the trans guy or the general public.
Trailbeast is right on the money. Contact one of the manufacturers and give them all the information on your setup and see what they recommend. You're not sure I see on what axle ratio you are going finally going to use and if you change it, it will effect the converters performance . Be HONEST with your information or you'll probably get a wrong converter. I've seen too many guys not be upfront when ordering a converter and end up disappointed. Abodyjoe has also given you some sound advise by saying go right to the source instead of someone who sells but does not make converters.