The 4.0 is a very strong engine - it won't "give out" because you boost it. I have 192,000 miles on my car with a blower on it since 90,000 miles. And I had a 75 shot of nitrous
on it for two seasons before putting the blower on. Still runnning strong, gets 12's at the track.
As far as the 7.5" rear end - replace it with a take off 8.8. Don't try to build it up, it won't last and will cost you more than a swap will in the long run.
Powerhouse makes a great turbo kit for the 4.0. A friend runs it on his car and went mid 11's this year. (PowerHouse411
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there are lots of 4.0's with forced induction (primarily Xchargers, but some vortech and prochargers in the mix too), and a couple of turbos. One of the members is coming out with a new turbo kit this year, she has been adjusting her kit and refining some of the components.
As far as turbo vs supercharger, what are your plans? Turbo is great for the drag strip, but not quite as much torque on the street, same with the centri supercharger. The Xcharger has great low end torque, perfect for getting out of the lane of traffic that is stopped and up to speed for the fast moving lane on the highway, gets out quick at the track but I stop building power about the 1,000' mark while the turbo and centri blowers are running me down and still making power.