(Going on your sig line I'm assuming your running 3" on 31's) Have you thought of just regearing? I'll bet if you where to drop a set of 4.10's in it you will realize numbers so close to stock you'll be happy. Something to remember is while yes being lifted will cost you a bit on the mileage your lift is mild, and the hight itself is practically negligible on the mileage number. Going back to the stock tire size, or regearing will gain better results.
Something else that will make a big difference on mileage is anything on the roof including the stock bars. They are a pain to remove, but I bet you would gain a mpg, or two out on the freeway. My father has reported a gain of two mpg on his 95 Town&county van by removing them. Another item that will help is a free flowing exhaust system. I was quite surprised how much power was gained by just replacing the stock restrictive muffler with a Flowmaster on my 2000. I never checked the mileage, but it had to of gone up. Just some things to think about.
Oh,and as far as OEM suspension parts. The only place I know of is Quadratech, or the classifieds