You'd be advised to locate some of the more hard core Jeepers in your area before you tackle something like this, as it is one of those "if you have to ask" questions.
Surf any local jeep aftermarket specialty places for leads.

The Hesco turbos are pretty good, but before you go turbo, check out the incredible variety of strokers you can buy from 4.5 to 5.0 liters [monster forged] including as crate engines from Mopar with about 265 hp.

I honestly don't recall ever running across a libby project running the straight six even back when the lunatic fringe was quite active on usenet.

As long as you don't get crazy, the libby drive train should be able to handle the 6--presuming the 6 will fit under the hood. Worst comes to worst, just do a body transplant.

To be honest, I'd be more likely to just project your Laredo. There's an encyclopedia worth of knowledge out there about doing this...

 

So you're saying it would probably be easier to mod the body as long as the frames good on the Laredo then to drop that big of an engine in that little of a frame?