X2 (keeps your numbers matching block). & Welcome aboard. Keep the heads/top end everything the same (& just enjoy the increased torque from the stroking). EDIT or get a 400 block & stroke it with an offset ground 440 crank (470 cubes) which wouldn't be prohibitively expensive & obviously keep your 383 stashed (this would minimize your down time). You'll feel the extra 100 cubes. with a B block (400) your exhaust system & ps/alt fitment on the front of the block would be the same. You could even keep the 383 pan/pickup.