64 rear end help

If this is your first attempt, I would not take on a rear-end narrowing job. You need to find a competent shop to do it because it all has to be done on a jig to ensure everything is straight and true. Axles can be custom order from companies like Moser and Strange to your custom specs. While you are narrowing the rear, you might as well do the spring-relocation kit as well and if you are going that far you might also want to consider a mini-tub job if you are really trying to get some decent tire under there.
-Tim