Torque Converter
Restalling a converter is no big deal, it's been done many, many times by converter rebuilders. You say that ACC says a 10" converter is wrong for your application, and if they have the information on your engine/diff ratio/tire size, they would know what is going to be the best stall. You might want to check with a couple of converter suppliers, give them all the information on your combo and see what they recommend.