As I understand it, the longer shackles put more leverage on the leafs (in regards to spring wrap) and can increase sag over time. A shackle should be matched to the leaf packs (as they do from the factory), not used to add height.
how much of a project do you want? It's totally possible to buy a whole car and swap in the fuel injection. But if you're not up to wiring all that, the block/heads are what you're looking for. :thumbsup:
go with the block from a 3.4L camaro/firebird. it's identical on the outside and will accept all your current accessories/intake/exhaust.
http://jeep.off-road.com/jeep/article/a ... ?id=277008
the front brakes changed. you'll need to keep the different eras together as a set. be sure to cap the vaccum source for the old front axle. Other than that, the front should go right in. :thumbsup: