I'm putting together a 69 Satellite with souped up 383 and a 4 speed.
I've read that the drive shaft length for that car is supposed to be 51.50 inches to centerline of 7290 yokes.
I have one from a 65 Coronet that is 52 inches to center line of the 7290 yokes.
I'm thinking I can use it for my project.
What do you drive line experts think?

I would mock up & measure how much free play you have (with rear end loaded)

Like he said put it in and see how much room you have.

I have a used 7290 yoke drive shaft at 51.5" and ideally I need a 52 to 52.625".

So if your mock up test is not favorable and you will be at Carlisle next week, perhaps we could trade?

Thanks for the input. According to the service manual I have it says the tubular length of the drive shaft for that car is 48.6 in. The flanges to the center line of the yoke measure 1.583 inches, 1.583x2+48.6 is 51.76 inches. I'm probably not going to be able to mock it up before Carlisle and the only reason I would go would be to get a drive shaft. According to Alaska it's probably going to work. With all that's going on I don't feel comfort coming to Carlisle. How about cutting the spline shaft a 1/4 to 1/2 inch if I need to?

The problem is bottoming out in the yoke if it is long and cutting it does nothing BUT you can shim the leaf springs back under the front mount around 1/2" or 1/4"

I have an NOS Mopar performance 7260 driveshaft NOS kit. Contains shaft with fixed yoke, tube, yoke, universal joint, balance weights. You cut to length and weld it.
It has a 29/30 spline slip yoke that fits a 727torqueflite. Prob still in the FS area for 2nd qtr. I'd make either of you a deal on it.

The one I have is not in the car, I am not going to use it when I know it's not right.

I didn't mention that I'm swapping and 8.25 rear to an 8.74 with 355 gears. I have a 56 inch drive shaft with 7260 yokes. I could take that to the shop which is about an hour away and have them cut it down. I'll need to get a 29/30 spline you as it fitted with one for a 904 trans. Then I have a small block setup in a big block 4 speed car and I'll still need to get a 7260 pinon yoke or a 7260/7290 adapter kit to make it work. Or have the shop shorten it and put the 7290 yokes on, or just have them make me new setup which may be the best option instead of some modified 51 year old stuff. A guy has a 52 inch with the right yoke for a 4 speed shipped for $215.
Another reason I didn't want to come to Carlisle is that it is 4.5 hrs one way and about $120 for gas and tolls. I probably can get a few other thing I can use as well. I could go up early Friday to beat the traffic and go home Saturday evening like I usually do then there is food to consider so let's call it $425 round trip plus the cost of the driveshaft which is nullified if I bring mine to swap with Alaska.
I think I'll get busy and mate my motor and trans, swap out the rears and mock up or measure the shaft to see what I need which I probably don't have time to do, not to mention the fact that a part I need that I ordered from Brewers is "backordered" as it needs to be modified by Dan who is too busy to get to it until he gets back from Carlisle the week of the 13th. The rest of the parts should be here by Tuesday and I could maybe get it together to figure out what I need but will have to probably take it apart to put in the back ordered B body big block clutch fork pivot which for some reason seem to be as are rare as "hens teeth" gets here. I could have got an "NOS" one from eBay for $45 plus another $65 for shipping and got the rest of the parts from AutoZone but I figured I'd support the hobby, but that's another story. It probably won't be too bad cause I have a 2 piece bell housing that might make the job easier roflmao.
It's not about the money, but it can be frustrating at times with so many variables not only to make it correct, but to make it right, safe and fun, which is all I'm looking for these days. I'm lucky enough to have the resources and time to pursue something I enjoy and am happy with that too. And in spite of Covid19, who knows maybe I'll see you at Carlisle cause in a addition to the driveshaft, I might need the correct 22" radiator and whatever else I'll need to make that work, oh yeah, some better bumpers, fenders, a stone shield, wheels, exhaust system, hens teeth, I know you guys get the idea cause with Mopar the possibilities seem endless.
Thanks again for your support guys.

Know anyone coming for sure that could make the swap for you?