Electra has the most luxurious trim, followed by Invicta, with Lesabre at the bottom.
Lesabre and Invicta 2 door hardtop bodies are similar, except for trim. Electra is longer and has a more "squared off" roofline.
Lesabre and Invicta have a 123 inch wheelbase. Electra is 126 inches.
Lesabre has a 364 engine, 2 barrel standard, 4 barrel optional. Invicta and Electra have a 401 4 barrel.
If you need more info, feel free to ask.