I sheared grade 8 bolts a few months ago. I noticed on the ARP bolts they have a nice flat land under the head that looks pretty nice and was bigger then the land on the grade 8 bolts ATI sends with their flywheel and spacer kit. Plus the ARP bolts are 41something chrome moly.
ATI has issues with the flex plate they sell. I reused my old one because the converter bolt pattern is wrong on the new one.
Always ARP. You should see the bolts that I got from one of the vendors. They are grade 8 with the heads ground down. Very scary especially when I ordered them with all of the face plated 9310 gears. Nothing leaves my shop wearing hardware store bolts, especially on the rotating assembly. ACE is not the place for flywheel bolts.
