making a truck bed traielr i got some Q`s

[Fast68Chevy]

those of you who have ever made a truck into a trailer, lemme know how you go abotu measuring where to cut the rails at under the cab floor and where ot notch and bend in the rails to meet at the hitch point and where to find or rob a hitch from and how to make sure it wil trailer straight without god legging or anything,

how accurate does everything have to be as far as cutting and bending in rails to meet at the ends up front ?

thanks for anything