Clifford Vs Offy

YES, you can use a clifford with a stock exhaust manifold!
The main difference between the clifford and the offie are the size of the plenum. The clifford has a much larger plenum and the runners start out much larger and taper down. The clifford is better for high rpm HP than the offie. The offie has a small plenum and the runners are small like a stock intake it is better if you are looking to have more low end torque.
SO do you want to do burn outs or drag race?