your right in asking and that's why, for ASE suspension certification: types of threads nuts and bolts are part of the study guide and book material. becaues it is a safety issue certainly.

 

you have a luxury situation here. you can take your best guess or pick of nuts. drive it. check if it's still tight. check it periodicall.

because it's not a customer car you don't have to loose sleep about whether they'll loosen. you can check and it's easily checke.d