89 k3500 have ifs also? or solid?

Easy question... I'm guessing so... I know the 1500's did in 88...

Most likely, if it is the new body style 89 it will. In 89 you could still get the old body style in work truck form though I believe and the SUBURBAN.

could go either way, depends if it's a r30 or a k3500. I think a K3500 will be IFS. I have had a few R/V 30 1 tons, they were all Dana 60's with kingpins. That is the old body style, they ran up to 1991 in the 1 ton trucks R/V series and Suburbans. But you could also get a k1500/2500/3500 from 88 and newer in the new body style.
a little confusing, i know.

if its an older style body and crew cab 4x4 then it should have a straight axle