Need some A-100 straight axle advise for a 66-valiant???

This guy is doing a Valiant gasser

That's kinda how I want mine, he's using like a speedway axle kit, I've got the factory A-100 straight axle that i'm gonna have to narrow... He also had his shackles in the rear, the dart I checked out in those other links had their shackles in the front... Guess i've got a lot of research to do on this little project...