I had a friend who had Loyde Rascoe install a 3800SC in an 88GT with a manual. On his way through Atlanta, he stopped to let me drive it. I can say that I saw 90 in 3rd gear. With the 4T sereies trannies, you can expect to get mileage equal to what you're getting on your 2.8 at highway speeds. Some have even said they get better MPG. I've even read that many people are getting 30+ with 4.9's.
The very popular 4.9 V8 is getting scarce, especially for a good low mileage engine. The 3800's are still plentiful, and probably at a lower cost. Though it's just my personal choice, if I ever did an exotic transplant, it'd probably be a 3800 NA since they're much cheaper, less likely to have been abused, they produce as much or more HP than the 4.9, there are a few go-fast goodies out there, and they run on regular grade fuel.
