Well this is what I know about the kit so far. BRP designed the mounts and tranny cross memberhttp://www.brphotrods.com/1978-1981%20G%20body.html
And Hedman desinged the header specifically for our G-bodies. As far as I'm concerned, this is the main part of gettin 'er in there.
As for what engine to go with, I was considering the LQ9 that's in the hummer, Escalade, etc. Iron block with aluminum heads. I heard it has a really good flowing intake even though it's not much to look at. The Camaro/GTO/Vette intake fits right on there with same throttle body and no mods that i know of. Plus the LS intake has a lower profile unlike the LQ9 truck intake. I saw GMs 4 barrel intake for the LS and might go that route. While i was nosing around Hedmans site, i saw they have fabricated LS valve covers and some billet coil pack brackets that look NICE. So it looks like we have a ton of options with this LS motor. A lot more than the LT1 which I've heard is a NIGHTMARE to setup. LSX anyone?