X Head Assembly & Installation - Comments Requested

I don't mind getting new bolts. Can I use grade 8 for a place lice fastenal?
No get the proper head bolts. The shanks have specific shapes. There is one head bolt hole on each side that has to have a narrowed shank to make sure the proper oil flow gets to the head; that flow actually goes around the shank of that specific head bolt in each head on its way to the rocker shaft.