Positive Camber Impossible?

On my 66 dart, redid front end, did not use the Offset bushings, and the alignment guys say it is impossible to get positive Camber. Searching the interweb, people are saying the original bushings were never able to do positive camber. I guess because they were using Bias radials?

Any confirmation on this? I am still needing the car to stay straight and give me a little wheel return when I do a turn. Right now there is NO return and the car wont return to straight.