As pointed out very well by Painted Jester, to build your HP goal with a 283 will be more expensive than with a 350. Any budget 350 build with a mild cam, dual plane intake, 600-750 cfm carb, and headers will easily make 300 HP.
Here's probably the easiest 300 HP there is for $1819.95 with FREE shipping and a warranty!
It's only $80 more with an Edelbrock Performer intake manifold
. You would be hard pressed to build it much, if any, cheaper.
For $160 more ($1979.95) you can get the 2 bolt main 350 Vortec long block
, again with FREE shipping. For $2019.95 you can get the 4 bolt main 350 Vortec long block
with FREE shipping. These both upgrade you to factory roller cam. The 2 bolt main block will more than handle the HP level you're aiming for. A cam change to the GMPP #14097395 cam used in the 350 Ram Jet and HT383 (High Torque 383)
engines puts you well into the range of your HP goal. Edited to add: This cam will work with the stock Vortec heads, lift is .431/.451, 196*/206* duration at .050" lift, 109* LSA (lobe spacing angle), really pumps out some torque in a Vortec headed engine.