I have a mid '80s car that originally came with a carbureted V6 and I was surprised to see that it had 3/8" lines. Your 383 should like it. The only concern may be with the original sending unit, if it has smaller fittings. When I put 3/8" lines on my 'Cuda, I also put in a new sending unit. If yours was originally 5/16", you may want to check this out too.