340 to 360 Harmonic Balancer Swap?

yepp the flex plate will work. are you puttin a 360 in place of a 318? there is a aftermarket flex plate to do that so you don't need a new convertor
"340 cast crank balancer is for a 340 cast crank...that is why it is written on balancer for 340 cast crank...."

Yes thank you. I should have thought of that. remember, everything is easy when you know how to do it. So it sounds like the flex plate off the 340 is good to go as long as I can get an oem 360 balancer and torque converter.