I've been debating this myself for a while now. Today I took my buddy to pick up his 99 Trans Am after he had a complete exhaust put in. Anyway, I asked the guy what he'd charge to install LTs in my 04 GT. He said that he hasn't done that model Mustang yet, but he figured around 4 hrs and $250. I mentioned that's about half the time that 99% of people say it takes. This is just a local mom and pop mechanic shop, but I'm thinking he doesn't know what's he's getting in to. He said he thought it would be pretty close to that since he does have a complete garage and that most people are just doing this at home. For $250, I think it's worth it to me. I'd just hate for him to come back after 6-10 hours and say I own some insane amount for labor.