Well, that worked great!
Used a large plastic bin and made up a strong lye solution, about 1 cup lye per bucket of water. Most parts cleaned up really well in an hour or so of soaking with a light scrub with a toothbrush.
Odd to me that the two dash sets I stripped were made from different base plastic, one grey, one blue. The instrument clusters were a -A and an -C engineering number, and had some slight differences in how the lenses for blinkers and running pony hi-beam lens were attached. As well as the fact that the -A was chrome on the back and the -C was not and painted an off white. A few other minor differences, but not in the base casting I could see.
I was surprised, as the cars were both San Jose Dec '67 builds and came off the line 6 days apart... no telling if the dashes were original but as they are FoMoCo correct and had the typical lack of chrome on the faces due to wear it would seem odd that they had been replaced...
Now to find a chrome solution, the local shop want $400... per dash, to chrome paint.... OUCH!!! Might be cheaper to ship to Ray, but they don't seem to answer emails.... tried to contact them a few months ago, no reply. And no reply to the recent email sent the other day...