I have a 97 GMC K1500 w/ 3"body lift and 35" tires.  I hav'nt broke an axle yet but I trashed my transfercase while trying to pull out a tractor and bush hog which I eventually retreived with a D6.  Any way I bought a transfer case, 1-ton IFS front end and a Dana 70 3HD rear axle for $600.  My current gears are 3.42 which are too high and I want to put the 1-ton axles in cause there 3.73's.  If anyone has done this I would appreciate any info on what u had to change? (steering knuckles, ball joints, etc...) I'd also like to get lockers for them before I put them in.  I think I want to go w/ air or E-lockers.  Does anyone know where the cheapest place is to get them?  Whem I get another vehicle for a daily driver I want to add a 6" suspension lift.  Would I need one for a 8 lug since that's what it will be after I change the gears or would it matter?

Any help or advice would be greatly appreciated.

I would ditch the IFS totally and swap a solid front end since you'll already be neck deep in it.  I don't think the 9.5" 1ton IFS will fit the 1/2ton frame, the diff housing is bigger and has different mounting points than the smaller 8.25" 1/2t IFS you have now. The rear should be fairly easy swap, spring perches should be the same width (or very close) and you'll need a conversion U-joint or a new driveshaft. I swapped a 6 lug 9.5 14 bolt rearend and had no trouble getting it to fit. I was able to reuse my original driveshaft with a 1330-1350 conversion U joint.

The front end will be much more complicated!