Based on my own measurements, and confirmed by a couple of articles I've read in the magazines, the firstgen has quite a bit of toe out under bump allready.
Running more positive caster helps to reduce it by lowering the outer steering arms, but it is still there to some extent.
If you have the springs out of your car you might check what you have now and see how much toe out under bump you are getting.
I don't have the article handy but I'd bet it toes out about an eigth of an inch per inch of bump. that's 1/16" (.0625") per side. measured at the tire tread front and rear at axle height.
It should allways be measured before ever thinking about fixing it.
When mounting the steering box and idler arm, anything you can do to raise them will help bump steer. the pitman arm side holes could be slotted to help. they are on third gen Camaros.
Otherwise, the only alternative is to bend the steering arm ends down.
Check my web page for First Gen Camaro suspension info:
David's Motorsports page
First Gen Suspension Page
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