I have a 63 two door post Chevy 2 Nova just last week I had the old motor(194ci) throw a rod so now im left with the age old ? "what to drop in its place?" I was thinking a mild 383ci with a 700r4 trans, but a 357ci or 327ci with a strong trans might work good. Its a project car but I hope to make it into a street sleeper. Any advice can help, your opinions count, and any additional info on the swap and other upgrades I will need to do to make the swap go smooth is appreciated.  

I think going with a 355 (350 bored 30 over) would probably be your best sleeper. The biggest thing about a sleeper is the exhaust. Don't make the exhaust huge keep it smaller so the car sounds stock still. For the carb intake combo your best bet is the edelbrock 750cfm and edelbrock performer rpm intake. The power range is from 1500-6500 which is best for a sleeper. Throw on some aluminum heads and run 10:1 compression and you'll be pushing about 400+ hp with some good full length hooker headers and maybe msd ignition.  

The 700r4 sounds perfect. I am thinking about putting that into my 74 Nova with a 389ci engine and about 1200 hp. For the rear-end you could do maybe a 3.55 or 3.73 posi traction to get better traction and more umph off the line without sacrificing a lot of mpg.  

I'm really fond of the ole 327 with it's perfect bore/stroke ratio (1.8:1)...
Or build a poor-boys 302 using a 283 crank and 327 block.
Another little known speed secret is the 377cid hybrid.
Slide a hydraulic roller cam in with some good heads and let her eat.
700r4 tranny with a gear vendors overdrive and 3.73's...
now that's a sleeper!