I hope the OP doesn't take offense to this, but this is the same situation we see time and time again.
Cost and value are NOT necessarily the same thing.
Fist it was said that they "need the money", then it was said "we just can't sell them that low" -referring to the value that was established using recent sale and no sale asking prices.
If you truly want to move them, price them accordingly.
I like this site for general (with exceptions) pricing info, and it does say 37K for a #2 car, however, by the OP info, they are basically nice drivers.
http://www.collectorcarmarket.com/collector-car/prices/1967-plymouth-gtx-value.html
I think the consensus is that a #1 basically does not exist outside of the "trailered only to judged shows with 100% original restored to stock and near perfect quality, and consistently judged in the 90+ point category", or thereabouts.
With that in mind, the OP has priced them at what amounts to full retail.
If you maintain a "near concours" asking price, you will be holding them for a long, long time and they will become "stale" to the intended market.
The "trick" is finding a realistic price that will move them.