I'm not followin ya. You should be able to buy an expandable anchor that will fit the hole size you decide to go with. So if you want to use a 3/8 anchor, you drill the appropriate hole, drive the anchor in the hole, then put the nut on and tighten to the spec necessary to set the anchor.
I'm talking about an anchor like this only not necessarily that size.
https://www.grainger.com/product/15X102?ef_id=CjwKCAjw1JeJBhB9EiwAV612y07G7IBOsKBmi OJe5bxThqyEN1oc4_wyl9OjnmBxmvcnYtku0b7r1xoC-MQQAvD_BwE:G:s&s_kwcid=AL!2966!3!281698275318!!!g!470148656870!&gucid=N:N:PS:Paid:GGL:CSM-2295:4P7A1P:20501231&gclid=CjwKCAjw1JeJBhB9EiwAV612y07G7IBOsKBmiOJe5bxT hqyEN1oc4_wyl9OjnmBxmvcnYtku0b7r1xoC-MQQAvD_BwE&gclsrc=aw.ds