I bought my taco 2nd hand and the bed liner has a change in shade markings of a box and no holes in the bed, so i would assume the box was attached to the bed rails with T nuts
HTH
Compilation of thing that I've done to the Taco in the past 2 months
1.) New Tailgate key cylinder (other discussions Why)
2.) Toneau soft cover (El Cheepo)
3.) Pair of M10 ring eye bolt for bed rail
4.) Bed Mat, a must have!
5.) Bed Divider (Hopefully we all know what it is, other discussions)...