Dynomax super turbo muffler size

I am looking to pick up some Dynomax super turbo mufflers for the car.

I will use the 2 1/2 inch pipe, but my question is what size muffler are you guys using? The 17748 is a 20" long case. Will that fit?

The next shortest is a 14" long case. 17733 I think is the number. I'd like to get the biggest muffler i can fit. I think the originals were 18" long.

These are case or body size only, not total length.

Thanks for any feedback.