Yes, they will fit.  He will need 4 slightly longer hold down studs.  T-Bird parts vendors have them.

John - "The Hoosier Hurricane"

I think the answer to this is YES but many online vendors do not show an application for 272, 292 & 312 valve covers fitting a 256.  But I find conflicting information.  I'm selling a pair to an owner of a 54 Custom line with the 256 police interceptor drive train.  He says they will fit.  Please advise.  Thanks in advance.