Yes and no... It won't work with the '70 grill, but it will physically fit on the chassis. In other words, you could convert your '70 to a '73 front clip, but you would need everything, hood, grill, fenders, bumper, etc.
Which Fender do you need?? I'm converting my 72 front to a 69. So I went round and round and round with this fender compatibility thing as well. I might have a drivers fender available. I say might because I got a 69 fender coming in the mail. If I don't need to use the 72 to patch it up, I'll be looking to get rid of it.