You don't say where you're located, but I have a 54 1/2" (center-to-center of U-joint caps) in very nice condition. 1310 U-joints and 27 tooth slip yoke have very low miles. Painted black. $150.
Good luck to you, racer! The shaft I'm selling was an inch or so short for my '69 SS with '69 M22 and '69 12 bolt so I replaced it with one that was 55 1/2" between U-joint centers. Not sure what the 54 1/2" one fits but it came in the car, back when it had a '67 12-bolt rear and a '72 Muncie M20 trans. Can't remember if there was too much of the slip yoke neck sticking out of the trans when I bought the car, but it did have a different slip yoke at that time, given the '72 trans had a 32-tooth output spline.Checked my rusty one, it's 55 3/4" center to center of U-joint caps, so I guess yours isn't compatible. Thank you however for the quick response, it's appreciated !