Welcome to the forum and yes do ask questions! We will be happy to make suggestions and give advice! The final decision is up to you.
I too would recommend the 3/4 ton axles due to the side drag when you turn. The articulating action puts a HIGH torque on the axles and drive joints.
Also talk to Gator on the u-joints! He had to make some heavy stuff on his so keep that in mind.
If you design in heavier parts to start with you will end up with a much more trouble free machine the first time around.
I would like to make a very light one using 2 sunstar 20 mower rear ends. I even kicked the idea around of going with just 1 and have small 2-wd model.
You will have to look around and compare designs and take the parts you like/want/need and design them into your build.
Keep us posted on your build! Thanks,

"A machine you build yourself is a vote for a different way of life. There are things you have to earn with your hands."