Does the motor have a PCV valve in one valve cover and if it does is it hooked up,if it does not the pressure from the motor will blow oil out anywhere it can.I found out this the hard way years ago,I took a 6 cylinder out of a 67 C-20 and installed a 350,I put aluminum valve covers on it that did not have a place for the PCV valve and it blew oil everywhere under the hood so you need to check the PCV system first.