The JDM DC 4-1 and the 98 Spec JDM 4-1 are virtually identical, the DC piece is basically a copy. The nice thing about the OEM header, is that you can add the heat shields, other than that, I'd probably, just on price and weight, go with the DC piece. But either way, you're gonna need the flange, the collector end of both are a 2.5 inch diameter, so you'll also need a special donut gasket, sometimes included.

Later,
Aj