The specs are in the shop manual and it is online at "Old Chevy mnanuals". You probably can't get a good idea with a straight edge. You need to put a mark on both tires and measure between them in front and behind the wheel. What I do is spin the tire and draw a chalk line while it is spinning. It is more accurate to use one mark. I assume that the suspension hasn't been lowered and the caster shims are installed under the springs?
