A 350 won't be a drop-in swap, but pretty close to it. It will build more torque than a 283, due to the 1/2" longer stroke. Feeding those extra 70 cubic inches will be painful at today's gas prices, even with some sort of Rube Goldberg squirter system instead of a carburetor. The next small block V8 I'm planning to build will be a destroked 305 with about 250 cubic inches, and enough valve train modifications to live pretty happily at 9K RPM. In your situation, I'd choose to build the 283, with a minimum of modifications, but I don't have to pay a machinist- - - -I've accumulated a bunch of tooling and a fair amount of experience over the past 50-something years. I just don't pick up big engine blocks and walk around the shop with them any more!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!