i just installed mine without the intake or exhaust manifolds. Now, if you do that make sure to COVER the exposed top parts of the engine so junk doesn't fall in. Of course this is a 4.3 and there's more room to work on stuff, but i have installed v-8 small blocks as well; The fuel pump, intake, water pump exhaust manifolds, distributor etc. can all be installed afterwards without difficulty.
i would recommend at least installing the, harmonic damper, timing cover, oil pan, any heat shields and the lower oil sender before dropping it in though.