The Utility bases do slightly differ from year to year ,you need to check blade clearance.
Just be careful when you use fluted blades on a utility as it depends on blade plate and blades ,sometimes I grind 1/8 of an inch off the end off the blades for clearance but mostly with the utility I get a big punch and hammer the side outward as the higher part of the flute usually rubs because the side of the mower tapers as it goes up.
From memory it's just one spot that rubs ,I've had a lot of utilities where the base wasn't panel beaten out and the blades have cut through the base in this corner.
With the muffler you can do as Norm suggested with a round muffler or do what Briggs and Stratton did when the muffler faces the operator, just screw on the deflector ,the deflector fits round or rectangular muffler.
