problems with truck darting around on road

[pete29]

i recently took my 72 chevy, that i'm restoring, for a test drive down the road. I had someone follow me behind and they noticed it was darting to the right a lot. So they drove it while i looked at it. What happens is like sometimes the steering lets go and it takes off to the right. or a brake is on one of the wheels but i don't think thats the problem because we can push the truck easily while in neutral. Any suggestions. Also the steerin is very hard to turn. I can't turn the wheels much eaither while its not moving. I've jacked it up and turned the wheels back and forth several times but that don't really help eaither. Any suuggestions on either would be great.