I'll have to follow the answers to this one, I can't see how radials can affect a wheel alignment. All the old cars I've had (lost count) would have had crossplys as original equipment, and usually its the first thing I change is to go to radials and I always have had alignments done at the same time without a problem.
If you want a challenge try driving with radials on the front and crossplys on the back, I did this once when I was young and broke (apprentice wages in the seventies) so I thought I'd get them as I could afford them. Couldn't drive the bloody car until I could afford radials for the back
Mick