Flexplate to torque converter bolt diameter

[Rockpig]

The bolts that connect the flex plate to the torque converter look to be apx 3/8 of an inch. The hole in the Flexplate looks to be aro 1/2 inch? Might I have the wrong bolts? Shoulder bolt? 1991 ho cherokee aw4. Bolts fit torque converter. I understand these bolts tend to loosen. Info appreciated.

 

[trippled]

10mm bolt? I can't remember exactly now. It's not shouldered but they do have a fairly low profile bolt head.

 

[cruiser54]

15mm head.