I'm pretty sure that the hi-lift blade comes with the 'kit' for mulching. It has 'Ears' on the blade where the original has two holes. The trailing edge of the blade, at the tips, has sharply turned up triangles of metal. At least that was what they sold me back when.
The ears on the blade are used to enhance the mower's vacuuming ability. I suppose you could use that blade for mulching, but it is putting extra load on the engine with no benefit. A single edge mulching blade is relatively inexpensive and you will be rewarded with less noise and less fuel consumption.
I found a couple of Snapper 28" mulch kits on E-bay and bought them. The kits had the "Ninja" blades they are a multi cutting surface blade,dull fast and are expensive($40+) I like the Gator blade, it's cheaper, cuts longer and dulls less often it's an all purpose blade ,vacuuming, mulching and discharge mowing.Having said that.the Ninja mulches a little better(while it's sharp) the hi-lift vacuums better ,but the Gator does it all.