in this case your best bet is to buy new pushrods and rocker arms. otherwise you will eat the cam. just curious, have you turned the motor over by hand to make sure its just not the position of the lifters that are making some more loose then others? so in other words if the loosness changes to different set of rockers as you rotate the crank then everything is probably fine.
Lets see what others say also.

the motor hasnt been started and run yet correct?