Its 4x4 5speed. the current engine is a 2.5 fuel injected engine. i don't want to have to change transmissions or beef up the differentials. if it is possible to swap engines what other major things would i have to change?
It is possible, however with your requirements like "I dont want to have to change transmission", then the answer is NO, you cant.
You can use a car performance simulator to virtually install the V8 with the 2.5 tranny and find out the performance, you find out how it would perform, try at http://www.nxgtrsim.com