If you decide to get the engine balance right, then you can put in a flexplate that has the external (im)balance and keep your non-weighted torque converter. I am rather curious why anyone would not put the right external balance parts in at both ends ....... ?? You may not feel it, but your butt is not a calibrated measuring device, and your crank is no doubt seeing added stress. If you lean on it, the price may be a broken crank over the long term. But, at least it is the 340; the external balance weights are much smaller than the 360; probably why it is hard for you to feel.
Here is a B&M external balance flexplate for the 340:
http://www.bmracing.com/products/10...71-to-1976-chrysler-dodge-plymouth-w-340-cid/
Compare that to the 360 flexplate to see how much more external balance weight there is for the 360:
http://www.bmracing.com/products/10...h-w-360-cid/?mk=40&yr=1973&md=287&smd=20&eng=