The additives won't do anything except make your wallet lighter. It's all snake oil.
The valve seats in the Mopars were a lot harder than the other cars back then. I've run thousands of miles using unleaded and standard valve seats with no issues. 80k miles on my A12 alone.
That's not to say that the addition of hardened valves seats is a bad idea when you are doing a valve job. It's just not a big issue like it is with other brands.