318 to 340 swap.

Only reason you would have to chance the converter, or flex-plate (assuming you already have a later 27 spline 904, or a 727) is if you 340 is a late one with a cast crank. They were externally balanced and the converters had balance weights on them. I know 1973 340's were that way, but not sure about 1972 ones. But not that big of deal. That make flex plates with weights on them so you can keep your converter. On the mounts I would change them to the Schumacher ones. Not cheep. But I just switched over to there polly lock mounts, and there torque strap. Now way I will brake another mount!! Boy are they nice, and worth every penny.