Driveshaft Length

Not all A-bodies are the same wheelbase. There's the 108" wheelbase cars, (early A Cuda's, Valliant's and 60's Darts I believe) and 111" wheelbase cars (Dusters, Dart sports, mainly anything 70 or newer I think). I'm not 100% sure on what all is 108" wheelbase and what's 111" wheelbase but I think that's correct. My guess is you have a shaft made for a 108" wheelbase and a car that's 111" wheelbase, but that's just a guess since you didn't state what car you have and what donor car the drivetrain is from