Rene, offset a-arm bushings are sold by most or all U.S Pantera vendors. Try (larrys@panteraparts.com) in Nevada. They are constructed with one of the pair of bushings having a 1/4" thick flange while the other has an 1/8" thick flange (measurements are approximate).
Obviously, if these are fully installed in an upper a-arm with the thick flange closest to the front bumper, the a-arm will be displaced back towards the driver seat and thus caster will increase. Offsetting only the upper a-arm will gain about 1-1/2 degrees of caster; added to the max possible with all the shims on one side of the upper ball joint, you'll get around 4 degrees.
The same thing occurs if you add another pair of offset bushings in the lower a-arms but with the thick flange closest to the driver, to offset the lower a-arms forward. For us, that gave too much camber, which increases slow-speed steering effort- unless you plan on installing some type of power steering.
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