We have done several but be warned--it's not a weekend job. You can get rear glass fenders that are 2 to 3 inches wider and that will allow a ten inch tire which, in the right compound, can handle 400 t0 450hp. This is of course with the suspension to go along with them. For the tubs you will have to cut the frame and move the rails inward the amount that will accomodate the tire width you want. You can use either ladder bars with a pannard rod or the 4 link, but in either case use coilover springs because space is at a premium. Depending on how narrow you go you will have to choose a spring rate that will give rear stability with the narrower track. Mount the coilovers as near verticle as possible and as low on the axle housing so you get the true rating of the spring and a lower roll center. No vehicle with a super narrow rear track and soft sidewall tires is worth a flip in the corners.

Evan