You can actually do it failrly cheap if you junkyard it. There are kits out there, but they are pretty high.
This is all the info you could possibly need to get it done. I am in the process right now, but with a 350. There is also a sticky at the top of the forum that has some info, but the link above is complete.
1984 CJ 7, SBC 350TBI, 700R4, D 300, AMC 20, D30, 35" Mickeys, 3.54 Gears, 4" susp. Lift, 2" body lift.
AMC 20 Write Up
In Progress - 4.56 gears, Aussie Rear Locker, Moser 1 Piece Axles
Coming Soon - CV Shafts, Welded Tubes, trusses