This is a fairly big project if you want to swap out the dash. I saw one that was done very nicely last night in Newington CT at the car cruise at Burger King. It had a complete GN interior. There was no roll bar or AC in the car. With skinny drag fronts and light weight racing aluminum rims in the rear id guess it could be as light as 3000 with no driver. Probably closer to 3100 with lightweight street rims and tires on the front and being able to drive comfortably on the street. I find it hard to believe it could be lighter than that without glass bumpers and hood while having the full interior in it. That is unless it has a bunch of other lightweight components on it like the front support, and lightweight control arms.
Turboelky says 2990 with the V-6. That is damn light. Wish my tanks were that weight. A 10.0 car becomes a 9.60 car with equal 60's. A friend of mine had a street race Malibu 10 years ago that weighed under 2800 with him in it! lexan windows, glass everywhere including the bumpers, stripped interior, no door supports though they were still steel shells, small fuel cell with an aluminum headed SBC in it with a lot of spray. The 3mpg was enough to make you hate it after one night of driving. It should have been on the trailer except to race. That thing was a real torture chamber. I always wanted to put in one of my v-6's and see what it would do. Trying to find an un-molested non rotted malibu is a chore itself. Good luck with the project.