The last time I was at the machine shop and I had my 340 heads done they told me unless I was driving the car a lot or use it as a daily driver not to concern myself with it. It never became a issue for the 10 years or so I had the car. Then again it`s your engine and you do what makes you the most comfortable. BTW, what year engine is it? I`m not 100% sure but I think Chrysler started hardening valve seats around 73 or so.