Get the short headder pipes that bolt onto your engine
Cut the headder pipes off the old muffler then weld the new ones in.
I do this a bout a dozen times a year
The muffler is a MOWER part & not an engine part so there are 500 different ones for each engine thus the quantity discounts do not apply thus the price is high.
Thank your lucky stars you are not down here when they can run to $ 400 ( Aus ) or more .
I can get a custom motorcycle exhaust shop to make me a stainless set up for around 1/2 that price .
Car exhaust shops will not have the flanges in the right sizes even if they have small enough tube