I was watching a old re-run of 2 car garge the other day and they did a turbo setup on this Trans Am. The turbo replaced the mufflers in the back of the car. There was a intake pipe from the turbo back to the throttle body. They claim very little to no turbo lag back there.

It got me wondering if putting an intercooler underneath the truck will work? Just need to do some plumbing, but I think it would be a lot easier to do that then to make the front intercooler. Just a thought

That sounds like it could be a very harsh environment for the intercooler. I would think rocks and road debris would tear it up pretty bad.