Stay with the 283, it will wrap up a lot quicker than the 350 because of the shorter stroke crank, and your desired hp range is easy to achive. The power is in the heads, so port & polish them pretty.
As for the "shorter" stroke crank- there are those in here that are stuck on stupid that can only think if it's written down for them. They will sit there & tell you everything that they have read out of a mag. somewhere & swear by it, mainly that a short stroke crank won't produce higher torque in a small block, yet they will tell you that a 427 is better to build than a 454 because you can get more torque where the differance is only the shorter crank.....hello??? It's the bigger is better mentality, and you can't help them- they are lost to their "set" ways.
Gasser has the right combo there, only go with a 40 over bore to keep from having heating problems, I went 60 with mine & it will heat in line at the drive thru.........
Good Luck