I really wouldn't bother with either.
Even though every other joker out there with a NAS 110 has to "upgrade" it in the same way.
The drums are fine. Really, they are.
They work well, parts are cheap and they last 100,000 miles. Where's the problem?
You may have noticed that you don't exactly have a fierce powerplant under the hood? Do you really want to make it labor against a slush box. Plus, as Ron alluded to the real key to an auto conversion is not mechanical. It's the trim. Without it, everything looks hacked.
Your truck is fine. Just enjoy it.