The 283 is a great engine, but the costs will exceed a 350 build. The parts availability for a 350 are also much more numerous giving you a lot more options.
The '57 doesn't have side motor mounts and are valuable to the right people. Find the casting numbers and the engine stampings and find out what kind of car/truck the 283 came out of. The right block might be worth the cost of a rebuild.
I wouldn't think that a high volume pump is needed with a 283. If you are looking to make some horse power and torque out of it, you are better off building a 350.
For the 283 you might want to consider making a nice driver out of it with a 700R4 trany behind it, a "small" 4 barrel, and an RV cam.
