I put an 04' GTO LS1 in mine, it will have clearance issues from the accessories as the alternator is down low, will hit pitman arm. Only substitute is to use the bird pitman arm, but will affect your steering set-up. Reread your suspension thread in the suspension section as Blake and Bonzo had things to say about it.
You can swap out the accessoriies with some truck stuff or a newer F body. I haven't done it yet as i may/most likely will be doing the clip.....
Let me know if you have any questions, btw mine is a 70' Cam...
Mike
Oh, and if you'd asked me two months ago about my LS swap, i would have said dont do it, but after driving it too texas from Bay Area, no question i made the right decision
and got 24.8 mpg at 80mph with 3:73' and T-56....