Holley sells a conversion kit to convert from mechanical to electric. The part number varies by carburetor, but go on Summit Racing and you should be able to find it. They
DON'T sell a kit to convert from mechanical to automatic, so if you're looking to go "original", you'll need to buy a 3923289 DZ (4053) carb. They're available reproduction but they're not entirely "correct". Read about the differences
HERE.
Ed