the gen 1 chevy 350 has a bore of 4.00" and a stroke of 3.48". when it's bored out to 4.030" then the volume works out to be around 355 cubic inch.
The 383 has increased stroke, at either 3.75" or 3.80".
best thing to do is google history of chevy small block and read read read. places like gmhightechperformance, hotrod, all those websites who have magazines are good sources of information.
the big thing with the pre-1990 ish blocks which are the generation 1, are their cylinder heads resulted in low compression at 8:1 and sometimes lower. the vortec heads on the later generation 350... the vortec 350... is the way to go and those engines put out 300 hp/tq reliably... and the vortec's had a roller cam, no mechanical fuel pump, one piece rear main seal among other things. they do sell conversion kits to put a roller cam shaft into a gen 1 block, in the end it comes down to cost and how much you want to invest in your gen 1 block vs finding a vortec block, and vortec heads and different vortec style intake manifold. but if you have a budget of a couple thousand to redo the motor and want to do it right, then look into aluminum cylinder heads and intake manifold setup... a roller cam is not the end all be all you can still do up your gen 1 block just as well using a flat tappet camshaft. the biggest influence is cylinder head and camshaft choice regardless of engine size, and choosing those things based on whatever the motor is going in to and how it will be operated (auto or manual transmission and rear axle ratio).
but don't overlook what was previously stated, you may be able to find a LS motor these days for the same price and have fuel injection.... unless you prefer a carburetor.