I would stick with a 350 as fueling a 383 with a TBI can be tricky unless you can find someone with a tried and true, proven recipe (cam, heads, injectors, exhaust and chip) experimenting can get you into a lot of trouble here.
The 350 TBI will take modest upgrades like an TPI L98 or Vortec L31 roller cam, another popular cam is the Crane 2030 flat tappet. To upgrade to the roller you will have to drill and tap the three raised bosses in the lifter valley for the lifter retainer (spider as some call it), and of course aquire the associated parts.
The stock swirl port heads can be worked to flow well (193 casting)
You can also upgrade to the IRON L98 camaro head which allows you to retain the stock intake manifold and EGR (unlike Vortec heads)
With any upgrades, keep in mind, that you will need to have a "custom" chip burned, but by doing so you can make a few changes like running a 160* or 180* thermostat, and have the speed limiter eliminated if your truck has it.
you can get an idea of some of the tuning issues involved if you look here
http://www.fullsizechevy.com/forums/general-discussion/performance/tbi-tuning-87-95-obd-i-ecm-pcm/