Need some guidance on transmission/flexplate/torque convertor
Ask the parts stores if they sell Daaco remanufactured torque converters. I put one like in the link below in a 71 Challenger with a warmed up 360 LA motor. The one in the link is the same specs as a Chrysler Hemi "J" converter. It worked well in my car. It's enough converter, but not so much that it doesn't work well in a street car.
https://gopnh.com/Torque-Converter-Specifications?AID=1295&perf=y