U-joints
 

so couple questions how hard is it to change the front u joints on the axle, and how much does it cost to bore and stroke the 4.0 average price I was thinbking like boosting it up to a 4.3 or something to retain decent gas mileage but boost the power a little bit. Now I am saving up for a performance package from rusty's which comes with intake, tb spacer, muffler and im also going to top it off with a header, so what increments can I have the 4.0 bored to?

4.6 liter

That's a stroker. Not sure of the boring displacements.

what type of gas mileage do you get? and how much? and where?

Front ujoints are easy. Remove you calipers and rotors, remove the three bolts that hold the unit bearing on the knuckle, give it a whack with a deadblow and pull out your axle shafts. Once out I used an impact to remove the hub nut. I then used a screwdriver, hammer, and a vice to remove and install the ujoints. Took all of ten minutes for both. Put it all back together in reverse order.

Oh, that's not mine, dude, sorry. I've got the bone stock 4.0 and get 21 mpg. I'm not sure with the 4.6 stroker. Start doing google searches for details.