340 cam 1000-5800 rpm... torque converter

I don't see any need to get more stall than what a stock 340 had from the factory. My new 1971 340 Duster, as I recalled, stalled in the 2200-2500 range. Contact some of the other converter suppliers that have been mentioned and go to their website. They should have a spec sheet for you to fill out, so they can build you what is needed. A 10" converter will be too much converter for you. The factory 340 converter was a 11" unit.