try getting 3 or 4 degrees of caster with the stock setup, sometime you cannot even get the stock alignment settings without the use of problem solvers.
Never been an issue with both of my A-bodies or other cars that I personally know and seen with offset bushings. Cars that can't get stock alignment with offset bushings have some car issue or an alignment tech issue. 40 years of mismatched parts, bad replacement parts, collision damage, and rust issues....
If you gotta move your K-member forward for 3-4 degrees of caster, there's something else not right or there's other options (adj: strut rod or UCA)