Its okay to use any bolts you want . Aslong as the shear rating in them is decent enough and you obviously get the correct length and thread . Sometimes it can be tricky to get some of the finer thread bolts . I generally buy to big and cut them back down to size ..
i have allen key bolts in my gearbox its much easier to put it in and out and .

Sent from my SM-G930F using Tapatalk