Here are some shots of my 65 Fords & some customs too . This casting is much more involved in roof swapping than past GL cars for making conv & hdtp swaps .. The conv boot is cut into the quarters & putting a roof on it requires a little filling in .. I also put the much needed whitewalls on the ones GL 'forgot' to .. Blue conv got a more correct blue interior than tan , & white hdtp got a blue interior - just like the one my mom had many moons ago ..
OOPS - Typo on headline - Wish the edit feature would let me fix that !!

These cars look fantastic!
Strange they would make the conv and the coupe bodys different.
The blue interior you painted really makes that car!!!!

I dont think the castings are different , but there must be an insert of some sort to make it different around the conv boot ..