Here's what i DO know:
1) the kubota flywheel is 12 3/4" but can be cut down to 10 3/4" easy. The stock samurai flywheel is 10 1/8". I dont know how the samurai flywheel would bolt up to the kubota crank block, else i would consider using it
2) finding time to park it and get going is impossible, but i may use a junker samurai for fitment as far as making an adapter for transmission and flywheel etc. before I attempt to put it in my final vehicle.

 

Since i can't put it in the truck, I just did some work on the engine today. I pulled the flywheel and housing off, did a few measurements for a rough idea. Put in a stiffer governor spring and backed the limit screw all the way out. If anyone else is doing that, save yourself some hassle and get the right length spring. I went about putting it back in the wrong order and it pulled the spring out of being tight. So I took the pliers and shortened it up tremendously, end result being a tight throttle that goes as far as it can. Don't know how itll affect how it runs, I havent ran the engine since i got it

 

I used a spring that was the same overall length and diameter, but thicker wire, works great.

 

It was the same length till i stretched it out trying to put it in there. thats when i shortened it and went about putting it in there differently