OEM/AMP Bed Extender question

Just bought a used OEM (Toyota sticker?) or AMP bed extender. Doesn’t look like Toyota is carrying the mounting hardware right now so I ordered the AMP kit from Amazon. Only comes with silver self-tapping screws even though it was advertised with a variety of black screws, nuts, and bolts. Came with a template so I’m gonna use the medium/small size template. Seems fairly easy. Tape template, use center punch to mark, and drill into the bedliner/bed.

I want to secure the brackets with nuts and bolts.

Does anyone know the size of the nuts and bolts if I want to take the taillights off and fully secure them ?

 

I attached mine on 2 different trucks with the self tapping screws. Never had a problem with them.