go efi.
when i built my 5.0 4x4 stick ranger, i originally went with a varb because i was not able to get the 5.0 EFI intake to clear the heater box (the TB aimed right at it), so i gave up and put a carb on it. last winter i was walking through the junkyard and saw a 5.0 HO cougar there and noticed that the intake curved forward 45 degrees and looked like it would fit. so i yanked the whole setup out of the cougar (cam, intake, wiring, sensors, and computer) and then yanked the carb and intake and cam off of mine (it was an 86 grand marquis motor, roller, but not HO). then i ordered a wiring harness manual for the 91 cougar from HELM and sat down and figured out what the computer needed and what it didnt. keep in mind that i have never done anything that extensive on wiring before. two weeks ago, after letting it sit all summer from being too busy at work to finish it, i cranked it up and it started.
its not quite as difficult as it sounds to put efi in it, but if you wanna keep your a/c, you will have to use the 91-93 cougar/thunderbird intake, or the identical 94-95 mustang gt intake.
after pulling the 65,000 mile carbed motor out of one of my oldies last year and seeing how hard carbs are on cylinder walls, i decided i would never build another one. pull the heads off a 200,000 mile efi motor and then pull them off a 75000 mile carbed motor....the carbed motor you would swear had more miles on it