My Father-in-Law did this to his '74 ( Ill see if I can find the Pics) They
were nothing special the ones he used were out of a mid 90's camaro/
firebird I wanna say. He cut a peice of lexan/plexiglass and glassed it in
Looked really really good. The only drawback was night driving they would
light up the stop sign at the end of the road, But not to much of the road
They sat to far back in the headlight housing. If that makes any sense I
guess it wouldent be too bad if you lived in a well lit area. Ill get more
Info on this for ya

Years ago... there was a company that sold body add-ons that also sold a
headlight modification kit.  You removed the riser assembly... and it was a
base that held the light and sat into the opening that remained.  It also
came w/a piece of Plexiglas that covered the assembly, sitting where the
door does now. I think they advertised it as a 'European lighting'.  I've
looked again, after all these years and can't seem to find it either...