Well i don't think the stock ic looks very efficient to me, but people have been known to make 400+hp through them. There are ic's with the style you're looking for, but I doubt you will find one with those dimensions. There's always 'custom made' if you want to go that rout. Besides, wouldn't that limit your mounting options? Just a thought, but in theory, you would want the ic as centered as possible and that might create clearance issues with the pipes hitting the frame rails. I've been using an ic with 24x12x4 core and terrible end tanks and I haven't had any problems.