I have two lenses in nice shape, but they have varying degrees of yellowing on them. Is there anything that can be used to get them back to a nice translucent white? I soaked one in dishwashing liquid and water; it got clean but it still was yellowed. Would a bleach solution work?

No, its not imported plastic.

I used a plastic lens polishing compound on my Tundras headlights. It removed about 70% of the yellow, saved me big $$.

Its a liquid, mildly abrasive paste that you rub on in circles and then rub off. Some kits come with buffing wheels for use in a drill. I do not know if it will work with 40 yr old plastic. I also have used toothpaste rubbed in circles to polish cd's that skip when played. That did nothing on the headlight lens.