Carriage bolt holes for wood bed

[Longhorn 69]

I just got my inner bed replacement pieces from Brothers in California. They have the Front and Back pieces for each side, short bed and long bed. they are 3" wide and have the square holes you are looking for. $40. each. They actuallyare the full lenght you n!eed and will fit in behind the wheel tubs and tie into your inner wheel replacement panel if you need them also. I'm working on them now but don't have them in yet. Drivers side is cut to fit now. Mar-K has some good parts and good info for the wood floor also.
Good Luck!