osxutils can do this for you with the help of "do shell script".
see command "setfctypes"
H =:o) L G I
> ------------------------------
>
> Date: Mon, 1 Dec 2008 18:41:47 -0500
> From: Mark Lively <[log in to unmask]>
> Subject: Re: help with resource forks...
>
> Ah.. its not that the resource fork is missing, its that the file type
> is being lost. If the files have the proper extension then the OS
> should be able to recreate it on its own. No idea of what it should
> be though.
>