The 296 looks like the same Pat kelley had in his 350 in his 67 elky and it ran 11.50`s. I would think that would performa better in your 383. That 304 mega you have in your 355 would work pretty well in the 383 as well. I know a guy who ran that same set up but less compression and it ran hard. He never had it to the track but he beat a 11.90 car on the street.