Correct the chryslers used 383rb early on. If memory serves correct the 59-61 or 62 factory hi-po 383 dodge and plymouth are siamese blocks the dual quad versions. I had a engine guru friend that built engines for dealerships back in the 60's and 70's that clued me in. We had one in the junkyard but I had to have a 452 stroker . So we went through and found a good 400 block. And he bought/traded for that 383 block. Hard to find info on them. Most people just assume all 383 blocks are the same