Correct, the lower corner is rounded on the door, so you either need 79+ ambi doors, or you will have to modify whatever you buy.
Go a tail gate, here are all of your options.
Aqualu makes 4 tailgates, two with storage and two without. They offer them in diamond plate as well as flat. They may look pricey, but they come with all of the hardware that you need.
Real steel cruiser parts makes two doors. One fixed that looks like stock. For 295 I think. And a favorite tailgate replacement for I think 525. You will need to source all o your hinges and latches with this tailgate. If you decide to buy this, you might consider marine grade stainless hinges and latches, and you will spend far far less. I can give you a link, or you can look in the dr slug thread.
You can buy barn doors. And modify the corners slightly. They will have a gap if you mount them in factory locations. I just verified that the barn door hinge will mount where the ambulance door hinge is. My plan was to modify the door and run one ambi hinge and one barn door hinge on the bottom.
Weiss design makes a cool fiberglass tailgate that says Toyota on it. I really wanted this at first. It is not very expensive at all, after customs charges from Germany, it was going to be 3 hundred plus shipped. You will have to source your own hardware for this. Again, I recommend the boat stainless stuff. It's a high quality piece. Germany has very strict requirements on all of its manufactured parts.
https://forum.ih8mud.com/40-55-series-tech/243444-toyota-embossed-tailgates-sale.html
See the picture of the red truck!
Sor and Weiss design sell fiberglass barn doors. I have decided to use these on mine and have bought a set. I am going to run them flipped so I can open the one barn door side while the spare tire is closed. These were 245 plus shipping. You will new all of your mounting hardware for these Toyota still sells the center latch, but does not sell the catch. I was quoted 34 dollars at my employee rates.
Several people have build a tailgate out o factory barn doors I have a basket case set I will let go for super cheap, of you want to weld these up and make a tailgate. You will find several threads on this.
Ccot sells a fixed tailgate. It's 100+
As you can see, I stewed over these options for quite some time.