IFS?
K2500 Suburbans up to 1999 don't have real IFS problems, 2000 and newer do and there are lots of aftermarket do dads to try and fix em!
The best upgrade is going to polyurethane bushings the black graphite impregnated type from Energy Suspension.
MOOG problem solvers are best parts for suspension/steering replacement.
Forged lower control arms are better than sheet metal type.
Upper control arms are not really a problem unless you abuse your rig.
Idler should be the 4 bolt type all others are weak.
Look under plastic cover to lower steering column just above steering box there maybe a rag joint under there and more likely than not would need replacement because of age and wear, if u-joints check em.
Bullet proof makes heavy duty tie rods and ends but in 400k+ I've not seen the need for them.
It is important to have steering wheel and box centered for proper function of GM variable steering gear.
Axle assemblies should be the large CV joint type.
Timpkin sealed wheel bearings.
1996/9 K2500 burbs share same year K3500 IFS components, not sure on early ones.
The K2500/3500 IFS 9.25" diffs are the same very stout and heavy duty, ARB/EATON make lockers for it, this diff should up under most conditions.
Ongoing debate solid axle vs. IFS. IMHO There is no need to go w/solid axle assembly unless going with tires larger than 35", 35" tires fit the K2500/K3500 w/o need for any lift but requires cutout fender flares.