I'm changing the exhaust system on a 70 RA III I just purchased. Was surprised to find that both manifold flanges were three bolt rather than the standard two bolt/three bolt setup. The casting numbers confirm they are 70 RA III manifolds. I want to change back to the original 2 1/4 pipes rather than the 2 1/2 inch system now on it. Can I use these manifolds and flanges for a 2 1/4 inch system,and does anyone know what the the dual three bolt flange setup is all about? Thanks in advance!