I agree with Hank, also I was looking in Leo's book, he say's if you "must" use a stock manifold, then use a HD-TD manifold on your STD-LD for street. He also mentions that not only does your manifold have provisions to run 2.5" pipe but it also has larger passages inside. I say you might as well take advantage of that extra flow, and (like earlier posts have mentioned) you can always go to smaller pipe at the exit if you need more backpressure.
