I have a 400 small block and im planen on using 350 heads, so does anyone know if i can plug the steam holes in the block so i dont have to drill the heads???????

NOPE. If you have a 400 block you have to drill holes in the heads.
if you dont it WILL OVERHEAT. Those cylinders are so close together they need that extra water that passes thru those steam holes to stay cool.

ok, but i bought the motor and it came with camel back heads and they werent drilled, but on the side of the block they ran coolent return hose that go up to the thermostat.so would the returns help it from over heating?
(the motor was ran in a sprint car)