Gary,
I have not heard the 30s, but I do use the 40s of the same vintage (w/upgraded midwoofer, TNT caps and spiral tweeters) for my mains and am very happy with them. I also use a set of RM2s for my surrounds and an LRC for the center. This makes a great HT system. I'd say pick them up if the price is good, even this vintage of 40s is hard to beat.
If you follow John's advice and use one of the 40s for center duty, I would be interested in purchaseing the other if you are anywhere near the Chicago area......
P.S. I will be traveling to Tennessee in April if you are anywhere between Chicago and Crossville