It may be that the 47-48 trucks with underbed fuel tank do have another cross sill under the bed. I vaguely recall seeing that the ones above the fuel tank were slightly different.
Hopefully someone with a 47-48 truck can answer your questions with more clarity.


Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.