IF you're using the fbody harness, you have a separate maf and iat. You can easily use the truck 5 pin maf.
Instead of the iat and maf being separate, they'll just reside in the same housing.
All you need to do is connect the fbody maf wires to the first three pins on the 5 pin connector. Then the last two wires are for the iat, I believe they are the purple and black or tan wire, but it's the last two in that combination, call me and I'll be glad to provide you with the 5pin maf connector and info on wire colors.
You definitely need the iat, if it's disconnected, the pcm will read -32 degs and think you're at the north pole and run very rich.
For you LS6 swap, I'd use a 2002 fbody pcm setup for the maf table, that'll get your engine running strong.

thanks and I'll talk to you soon,

allen