1965 classic v8 2 piece propeller shaft

No; I would not expect that rear flange to come off the shaft

Is this another basketcase car that has been taken apart for many years?

IE: Are you certain the center carrier bearing must be replaced or is this just another excuse not to put the car back together (car's name is Humpty Dumpty?)

-please take no offense for second guessing your diagnostic

Yes; the splined area is where it must come apart.

I'd say it'd be good to at least locate a 'plan B' spare driveshaft just in case yours gets destroyed.

Two junkyards here in Texas should have one: John's Salvage in Seguin, Tx. and CTC Auto Ranch in Denton, Tx. -both junkyards have websites.

My first thought is, since it's stuck, and become a one piece driveshaft by corrosion formation (iron oxide/rust) I would begin to figure out how to make a spreading fixture that would use 'worm screws' to apply spreading force to the area while using a torch to heat the flange on the tubular portion. It may take a lot of heat until you can see oil bleed into the (cherry red/orange) slip yoke area. Even then, I expect it will be very difficult to pull the stuck splined area apart ...without some type of custom made spreading tool.

I think you are going to need a lot of 'good luck' to make this happen. IE: lots of patience and perseverance, trying one hundred different ways in order to get your desired result. IE: you must totally reject the idea of becoming defeated/giving up.

Tasks like this 'build character'. Lets see what other people will say....

...on second thought, it all might be easier if you simply cut the tubular portion in order to press out the splined shaft, then have the tubular section re-welded and rebalanced at a driveshaft shop (shop who works on Jeeps should know where to get the driveshaft re-welded and balanced)