It is basicly your choice because they all have wins and losses in there own ways. a 400 engine is somthing me personally wouldn't bother with, because of the siamesed bore's and steam holes in the heads, people do build them up sucessfully. a 383 is going to lend you lots of low end torque and lots of power because it has a large rotating mass, as a 383 is a stroker. a 350 can be built up also, probably the best if you want a daily driver.