Outdoor Power Equipment and Small Engines - Swapping Blade adaptors

Someone gave me a Honda Harmony Lawn Mower HRT216SDA. It is self propelled. The blade adaptor seems bent to me and there are no blades. This mower takes the two blades. Can I put another blade adaptor on and a regular 21 inch mower blade. I would probably use a MTD blade adapter from a late model Bolens Mower as the adapter is pretty heavy and I can easily get a new blade to match. The crankshaft seems to be ok. The Honda blade adapter is $27.00 and the blades are approx $25.00. I can save a bunch of money this way. I have never done a swap like this before.

The other adapter should work OK as long as it fits the shaft properly, has the same keyway dimensions, and the same size hole for the bolt into the crankshaft.

The adapter should be a tight slip fit onto the crankshaft with no play at all.

I would think that the crankshaft is either 7/8 or 1 inch like all other mower engines so the fit over the crank should be ok -- no ??? The real test is the keyway and the shaft.

Something else to think about is the position of the blade relative to the bottom edge of the deck.
Most push mowers are engineered such that cutting edge of blade is approx 1/4 "+ above the bottom edge of the deck.

I doubt the crankshaft is standard dimensions. Probably metric.