What's with these flexplates?

[ootdega]

I've been looking at all the OEM Ford AOD flexplates, and a lot of them have different numbers of oblong holes cut into them. Some of them are solid, others have anywhere from two to eight holes in them. This even seems to vary within the same year and model. Anyone know why?

Here's what I'm talking about:

[gadget73]

supplier changes and balancing efforts if I had to guess. If you notice, the welding marks are opposite the large cutout. The second one is flipped the other way and you can see the weight attached at that point.

[ootdega]

Interesting... I wonder if that would have a long-term effect when used on a different 302.

[gadget73]

as long as they are the proper imbalance weight, it should be fine. They didn't dynamically balance the engine as a complete assembly. Race motors might, but not mass produced factory stuff.