You will only be here once so why would you do anything but restore it the way the factory did. Painting the undercarriage body color is as bad as painting the trunk with spatter paint or the engine compartment black. It's all WRONG!
There are plenty of products that will protect and have the appearance of the original correct look from the factory.
To the OP. If you have a GM guy restoring your Mopar you will have a ton of problems unless you watch him like a Hawk! Do your research and make him do it the way you want or on completion you will be disappointed.