I have afew questions about making pivot strut rods (materials)

David,
A 3/4" grade 5 will be able to handle the tensile and other loads placed on your parts. Grade 8 will give you a large safety margin but is not necessary in that size.

You can't gain much strength by adding 1/8 0r 3/16" metal on the outside of the clevis. The two parts do not add their strength - the stronger one will fail and then the weaker of the two wil fail with it. If you have the resources then just make one out of tool steel and it will be more than adequate. Do not use mild steel to fabricate your clevis.