Happy SLP guy here.
Here'* the scoop. They will bolt right on, and if you toss on a 3" cat at the same time they will almost come to the point of the firrst exhaust hanger under the car. Not sure where Jason (Bonnemn) is getting the info on the downpipe. It is part of the rear header piece.
You will need an O2 wire extension and a W Body trans filler tube, beyond that it'* straight forward.
On the front trans mount, something needed to be done in my case. The mount has a baby strut on it to help with engine flex when you stomp it. I found that too much of the ear would have been removed to keep the strut in any capacity. Hence...a solid motor mount was developed.
(If you'd like more pics, just holler)
Two things to keep in mind when fabbing on up is the block has an out jutting area and the subframe is close 1/8" below the bottom of the bolt in my mount. I've been using it for over a month now and so far love it.