David ,
I'm thinking you must know what you have in these pieces , add in an appropriate mark-up (say $5.00

) and presto!
Seriously ,this was proposed ,if I remember, about two years ago
and the responce was pretty good. I am pretty sure if the cost of these pieces was reasonable enough the hassle of the retro-fit would readily be over looked. I would also think that after a couple of any particular car had been retro fitted (say Contemporary

)a retro part kit could be put to paper if not actully " fabbed-up" by some enterprising individual.
I know a lot of us with older cars are looking at a body off repaint
soon ....................there is a definate economy to this ...........
Just my thoughts Karl