Lwb cross sills (help!)

[Mr.Hyde]

Well it's getting late here I don't wanna leave a job half finished so here's the big question on the longbed there should be 5 large cross sills and I only see enough bolt holes for 4 and I guess the small support sill. Where is this goth cross sill near the rear supposed to be they are the number 3 sills according to the lmc catalog but give no further help. If I had my computer not accross the city I would research it but if I could get some quick help?