A lot of difference between those two headlight wise. What exactly are you working on and what time period is the build going to be?
It's the car in my avatar a 1939 Desoto coupe I want to do something custom I really like the 40 willys and 40 ford lights I will be making a custom built one piece hood for it .
Frenching 40 Ford headlamps does not involve using the beautiful 40 DeLuxe chrome doors that I think you find so attractive. Same with the 40 Willys. What you'e going to be doing with these is simply replacing, or placing, the complete assemblies into the empty holes in your fenders and determining how much metal or filler work you're going to have to do to make it happen. Frenching, in its purest form, is sinking the headlamp bulb and retainer ring back into the fender literally or using another make's (usually from early 50s Fords or Mercurys) headlamp door and welding it to the front of the fender so only the face of the bulb and edge of the retainer shows. This is done to improve the visual of the graceful front fender curves with the least distractions. Frenching taillamps is much the same except ofttimes the rim is retained and sunken flush with the surrounding sheet metal. Sometimes the sheet metal is made to form the retainer rim and the lens only is visible when the assembly is mounted from behind the skin of the back panel or fender. Tunneling is often mistaken for Frenching today, but is totally different even by simply the name itself.
I am sorry about my first post what I meant to say was I would either like to use custom round Frenched headlights or change them to 40 ford or willys and I'm leaning towards the 40 ford or willys more I think it would look tuffer with the tear drops. I will post in the for sale that I am looking for the 40 ford or willys complete headlight set up