Hi Don,
It's the hub that needs to be slightly offset to the right to allow additional room for the brake disc on the left - not the rim.
If you have a cast 16" or 18" front wheel and suspension forks, there is not much that can be done to reduce the offset. I may be possible the tweak non-suspension steel forks slightly to reduce the offset.
However, the cast 20" front wheel should be correctly centred if GM have followed
my suggestions correctly.
A spoked rim can be offset slightly to the left in relation to the motor, so it can still be correctly centred between the forks provided that the spokes have been correctly adjusted and tensioned.
If you have a spoked front wheel and your rim is not centred between the forks, it should be possible to adjust it
(after making sure that the wheel has been installed perfectly upright in the fork dropouts) by adjusting the spokes to bring it into the correct position.
I would start at the valve and then slacken in turn the nipples of all 18 spokes on the side of the rim that is closest to the fork one complete turn until I reached the valve again.
I would then tighten each nipple on the 18 opposite side spokes one complete turn until I reached the valve for the second time and then check the offset.
You may have to repeat this process several times
(using smaller or larger adjustments as necessary) until the rim is properly centred within the forks.
Hopefully you can understand what I'm trying to explain.
Alan