bed cross sill location?? I need help!

[64GMCHorsepower]

I am finishing up my bed, and am not sure where the cross sills go:

I have a 64 GMC short Fleet

I have three cross sills and one support brace

1) I know one goes by the front headboard
2) don't know where it goes
3) one goes by the rear cross sill at the rear of the wheel tubs

I also don't know where the support piece goes (It only attaches the bed wood together, and does not attach to the frame)


I thought I had some pics of when I took it apart, but the ones I found were no help on the middle braces.....


Thanks

Chad