Alignment Problems

You should shoot for positive caster as the Skosh chart shows. If their stock bushings most likely you won't be able to even get it to 2 degrees positive caster. When they designed the steering on these cars bias ply tires were used and didn't require that much caster so the steering was designed to adjust in the range the tires worked. Only 2 remedies are possible. First being the offset upper control arm bushings OK mentioned. The other are aftermarket control arms that are designed for more positive caster. I haven't done enough front end alignments to know if it's possible the steering axis inclination issue may just be related to the negative caster setting and your alignment machine being much newer doesn't like those settings or it is possible you have a bent spindle or control arm. I thought that warning only shows up when you can't get the alignment set equal on both sides, but again my actual experience aligning front ends is limited. Since you work at a shop where you have access to an alignment machine try setting the caster for as much positive as you can get, (I could only get about 1 to 1.5 degrees positive out of mine with stock parts) and see if it still kicks up the steering axis inclination warning. If so, does it say if it's just one side, or does it specify?