36" can work - it would require the toilet on the 36 inch wall, a door in the middle (maybe pocket), and the sink opposite the toilet on the other end. So, 36 inch wide and 7 - 8 feet long.

I made ours 3'x7' with a pocket door in our new build. Full size toilet, sink, and custom vanity. It's a good good size:

Unfortunately, it looks like I'm only going to have about 6'3" clear length wise. I'll end up with a 3' x 6'3" also with a pocket door on the side.

@Robert - You've got 75 inches - It could still work - you need to check code clearances in your town. There needs to be a certain amount of clearance in front of the toilet to the sink - usually 24 inches.
https://buildingcodetrainer.com/minimum-toilet-clearances/. So with proper planning you could make it. The Toto Drake elongated toilet is 28 inches deep, 24 inches of clearance, and the Kohler Memoirs classic pedestal sink is 20 inches deep, for a total of 72 inches. You've got 3 inches to spare. If you select. you fixtures correctly you can do it. You could even use a round front toilet to save more space.

Looks like my issue may be my length (6'3") restriction more so than width.

@Robert - Check above - it can work.

Thanks for the input. I'll research the toilet and my sink/vanity.

@Robert - There are plenty of narrow vanities to chose from depending on the look you are going for. Make sure you have the 75 inches WITH the drywall. If not, then toilet or sink will need to be shallower. However, it can work.