If you don't mind changing from a 289 to a 302 there's plenty of choices. A 302 doesn't know if it's in a truck, Lincoln, or a Mustang. To keep things simpler, look for pre-80 midsize cars, Tbirds, Mustangs, and LTDs. And some others. These will be carbureted cars and usually have a C4 behind them. If you don't mind some more work, you can look at 80-90's cars, but they will be fuel injected and will more likely have an AOD. You can use an EFI motor by swapping the intake, oil pan, timing cover and some other stuff. Or you could convert your car to EFI, but it's complicated and NOT cheap.
If you're looking for a good 289, good luck. They quit making them in 68 and they're getting rare.
Look around and see what you can come up with. Many VMFers will gladly tell you if what you've found will work out and what you'll need to make it work.
I bought a complete wrecked LTD wagon one time for $200. We robbed the 302 and AOD for SWMBO's Mustang and sold the rest of the car for $50. This is likely the cheapest way to get a good deal on an engine.
Thanks for the replys , but I dont think your understanding the question. I dont need a new engine or trans I just need a driveshaft that will fit from the rearend to my c4. The output shaft on the c4 is a 28 spline shaft if that helps any. Thanks