360 flex plate

ok guys. looking for info. short story is I have a 727 from my 340 I want to take that tranny and use on my brothers 360. I saw some dudes use a flex plate that is balanced for a 360 does that mean I can use the torque converter from the 340 or do I still have to buy the externally balanced torque converter for a 360, just trying to shave a few dollars off this build.