I'm not sure what length a 70 Duster 4 speed driveshaft is. I have a 67 Cuda with a 360 engine, 727 trans and an 8 1/4 rear end. The driveshaft I have now is 44 1/2 inches between ujoint centerlines and the slip yoke isn't in the transmission far enough. If I can find a small ujoint driveshaft 2 inches or 2 1/2 inches longer that would leave me with 1 inch to 1 and 1/2 inch free play before the slip yoke bottoms in the trans. I'm trying not to have a driveshaft built because I'm more than likely going to put a big block in it with an 8 3/4 rear in the future and would need a different driveshaft at that point. I was hoping someone had something laying around that would work. Thanks.