A 283 with a 327 crank is a 307. There really isn't much reason to lose 50-100 cubic inches when performing an engine swap. If that 283 has been fairly modified and does in fact perform really well it wouldn't take very much to make a 350 perform at least as well or or far better. Remember that extra cubes means more torque and that in the case of a 283 and a 350 you're talking about as much as 70 lb-ft. Short of forced induction, what engine modification out there is going to give you that much of an increase? If you're willing to spend the money on a 383 or 400+ inch engine then go that route because there really is no comparison in what a 283 can do vs a 383. At the very least, stick with the 350.
If you're running on the car on the street, stick with a tranny that has more than two forward gears in it.
If you're running on the car on the street, stick with a tranny that has more than two forward gears in it.