bolt head id on 1969 body

1 and 2 I have no clue on. What do you mean by "E" and "I/C/S" bolts???

3. Yes. 3/8" lock wacher in some places. 3/8" flat washer in other places.

4. ??? What do you mean "what is on the head"?

Are these question are do to you doing a concours restoration?