Is it possible to swap the rear pattern back to 5x4 without swapping rear ends? Can I put new axles in it? Maybe chromoly for some extra strength. Gonna keep the slant six but try to modify it slightly.
Not with factory parts. You might be able to have some axles made and then you would have to deal with the brake drum issue. Much cheaper and simpler to get a 7 1/4 sbp rear end because nobody wants them.
Your other only possibility would be to have some custom billet aluminum adapters made.