rfs324

So I bought a sr20det bare block, thinking I would tinker and try my hand at building it while waiting for my KA to blow up. Previous owner had no information whatsoever. Is there a way to identify the engine from just the block? Some forums say no way to tell some say kind of. Does it even matter? Are all internals interchangable? How about heads, will an s13 head work on a s14 block and vise-versa? On here some people say that all the internals are interchangable, others say no, others say yes but with modification to the block.
Thanks yall!