straight axle choices?

ive got a 63 and was wondering if anyone knows what straight axle would go into my car the best, what track width should i be looking for, shackle to shackle, pad to pad etc. heading to a junkyard a few hours out this weekend, they have ALOT of stuff from 30s-60s. so if anyone can give me any ideas of what to look out for that'd be great. any help appreciated.