I got mine on Ebay, but it was specifically designed for RB20/25 swaps in our 240's.... I haven't seen them on Ebay in over a year... I'm not gonna lie, this thing fit perfectly, with a 3 inch diameter and didn't get in the way of the steering rod. (plus it was only 125 bux!!) But, like I said, i haven't seen them listed since early last year..
Anyway, from what've read the SR one's won't just bolt up to teh stock cat location, and I have no idea if they will clear the steering shaft.
Your best bet is to try
http://www.phase2motortrend.com to see if they still stock their rb dp for $250. That's not a bad price at all..