383 is considered a big block, as it's the same as a 413, 426 wedge, and 440 block. You can make some serious power with one, but they are expensive to build. Even here in the states. I would keep a Mopar in it, but that's just me. Maybe a SB like a 340 or 360 CID. In reality it depends on your budget, availability of parts, and what you want to do. A nice mild 350 SBC would fit nicely with what you want to do. AS far as tubbing, unless you just WANT the pro street look it may actually slow you down some at the 13 second level. I've seen cars go well into the 10s on slightly moddified stock suspension, and 10.5 inch tires.
