I am in the process of gathering the parts to redo the rear suspension on my jeep. So far I have MW CJ springs/Revolver shackles and ruff stuff shackle hangers. I want to extend the wheel base as much as I can using the parts I have with out sectioning the frame. Can I just mount the spring/shackle mounts farther back? I am thinking about mounting the shackle hanger under the rear bumper, that would be 3-4 inches more than what it currently is. Doing this though would place the spring hanger in the arch of the frame. Is that a problem? Am I on the right track? Is there a better way to do this using the stock style parts?

Use a longer spring, xjs work well. Lose the revolvers.

you should mount your rear shackle hanger on the back of your bumper, not under your bumper.
XJ springs are 51" long and stretch your axle back 4". dakota leaf springs are 54" and stretch your axle back 10".
this will keep your front rear spring mounts where they are.

I had thought about mounting the shackle hangers to the bumper but thought that it would interfer witht the shackles movement.

as long as your shackle angles are at 45-50* you are golden.

really bad pictures I know, but this is kinda what it would look like. I think if I mount the bracket to the bumper the top part of the shackle will be on the bumper.

http://i16.photobucket.com/albums/b23/militaryjeepin/bumperfinished015.jpg
http://i16.photobucket.com/albums/b23/militaryjeepin/bumperfinished014.jpg

either weld that new mount lower on the bumper, or flip your shackles around.
or do it the right way and get rid of the revolvers.