Might want to look at Hagans, they make a set of Caddy looking lights with the buckets, bulbs, and lenses.

Can build it all yourself, as far as how much to french probably not much on the tailights... Some cops that actually pay attention may notice the fact that the further they are frenched, the less they are visible from angles behind the truck. On tailights, I actually prefer to do the whole project so that the lens winds up flush mounted to the surrounding surface....Helps with the visibility issue....

Some place in my gallery is a picture of the Merc in grey primer with the tailights flush mounted.