i orderd a 31x12x4 FMIC core is 24x12x4... 3" in/out boy its large...
I orderd a DIY kit off ebay, quality is decent. 3" bead rolled boost pipes, except for the u-bends, silicone couplers, t-bolt clamps.
also got my edelbrock victor series muffler..4" inlet/outlet. has two 3" (approx) split flow tubes in it. ceramic packing etc
I plan on running 4" fom the downpipe all the way to the rear of the car. we'll see..
by the way, if you want a muffler like this(only 4"), edelbrock has a closeout sale on there website... i got this muffler for 50 bucks!