Another alignment thread!

I believe your alignment guy saying that's all he can get. Before leaving from CA to OH in my 68 I had it aligned because it was way out of whack. IIRC, the guy could barely get the caster to zero let alone positive. It worked fine driving the 2800 miles home.

A few years later I rebuilt the front end and used the Moog offset "problem-solver" eccentric bushings in the UCA's. Installed to provide max caster. These allow for additional range of adjustment unlike the stock concentric ones. Caster 2* positive, camber .5-1.0* negative, and 1/16-1/8" toe in. Car tracks hands-off like a freight train and is very stable in the corners. Do NOT use the original alignment specs as they are outdated for use with radial tires. Your negative caster is most likely causing your wandering.

You didn't mention what tires you are running but if not in excellent condition they could be adding to the problem. If it was me I'd remove the UCA's and go Moog offset and realign