Wood bed installation

[OregonNed]

I haven't made any careful measurements yet of my existing truck bed, but has anyone replaced theirs using board dimensions different that what came with the truck? I'm just wondering if cross rails can simply be drilled for the difference or if anything else might keep this idea from being simple.

I have some great looking wood, but I am having difficulty coming up with enough boards to meet the 7 7/16 measurement for my wider boards. My thought is to forget about the 5 5/16 (I think that's it) boards and go with something narrower than the existing wides, and more uniform across the bed.

My truck is a '68 long fleet side.

Thanks!