Chris,
99% of those clear lenses are/were melted from the running lamp bulb. The lens was double-curved to match the metal lamp bucket housing, had a molded rubber gasket, and three tiny machine screws with formed threaded metal "nut" pieces that clamped the lens on the inside. Doubtful that the other lens shown would fit correctly.
As I need several of the correct lenses myself, I have given thought to flat-cutting some Lexan, hand-carving a molding buck out of wood, and carefully baking in an oven until the Lexan slowly sagged onto the wooden form. Not high on my to-do list right now, but that's the plan unless someone else beats me to it, and hopefully creates extras we all can purchase. Running a low-heat LED lamp would prevent future problems--hopefully.
These early 45 lpb lamps were also used on the Toyota Stout pickup, and some early Australian 40 series. The later 45 pickups used the commonly-seen wider three-color tail lamps as on the 40 series, and so their rear valence had wider openings stamped into them to accommodate. These wider lamps could be used in your case if satisfied with them sitting flush on the valence surface, and not inset.
Other option is to use two of the non-license window lamp buckets, and a separate and different license lamp setup for the rear license plate, as was used on the later 45 pickups.
Because I am OCD and tinker with stuff, pls let me know if you decide against using your lamp bucket, and I would consider buying it from you.
