Robert,
What you describe is bump steer, later cars had spacers to lower the rack and bring the rack ends/tie rods more parallel, so that when the suspension compresses it doesn't alter the wheel direction. Check your rack for the spacers and the angle of your rack ends/tie rods. Bump steer kits are available from the usual vendors, or you could make one fairly easily. A good alignment shop should also be able help resolve this.
Here is Mike Dailey's page on bump steer and resolving it. http://www.panteraplace.com/page135.htm
Good luck,
Julian
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