Everyone does them different so there is no exact answer. Ive always used the 79-83 main leaf because both eyes have the same size bushing and always seemed to me to have a little more arch. Then use factory military wrap for 2nd leaf then the leaf with the clamps for 3rd. Then with another set of toy springs i cut down main leaf for 4th spring and cut military wrap for 5th and cut clamp spring for 6th.
My springs sit about 2 inches from flat and ride well. Ive seen people running 3-4 leaves alot and they usaully seem really flat or slighty negative to me. I would just find another set of toy springs and cut one leaf down and see if it gets you where you want. I believe the 3rd gen toyota springs are wider and im sure are longer so you may try to find a pair that matches the width you have of ot matters to you.
I have my bumpstops set to where the springs are flat under compression. Im a firm believer in not letting them go negative. Have been running the same set for about 8 years and they still look and ride great. You can set your bumpstops as your truck is. Adding to your existing spring pack will not change where you want your springs to stop at.