replacing your front springs with another set of front springs wont give you any results. all you need to do is find some rear springs and take a couple leaves from that and install them in your front spring packs, this will give you more than enough lift.
OH and your first gen will easily handle 31's with absolutely no lift at all.
No, using long shackles for lift is NOT a good thing, especially in the front, not so bad for the rear.