My friend has a .308 PSA 18" mid length upper that he wants me to put a Midwest industries free float rail on.
My question are:
1 Will the upper fit in my upper block so I can change the barrel nut? I have both types the pin type and the hinge type both for 5.56 uppers.
2 The rail comes with a barrel nut wrench but will my standard armorers tool take the .308 barrel nut and delta ring off?
3 Don't need it for this but just curious abut my mag block, I know 308 magazines are bigger but will a .308 lower with mag catch installed grab on my 5.56 mag block?
Thanks for the help!

1-No. The receiver on an AR10 is larger diameter and the pin spacing is different.
2-No. The barrel nut on an AR10 is larger diameter.
3-No. Too much slop. You can whittle down a piece of 2x6 to work.

Keep in mind on an AR10 your barrel nut torque is higher. Something to consider if you plan on holding the upper by the pin bosses

That is what I was afraid of, thank you  for your help.