Outdoor Power Equipment and Small Engines - Craftsamn-Tecumseh Replacement Motor?

I just inherited a ~7 yr old Sears Craftsman propelled lawn mower that is basically in pretty good shape - except the motor is kaput - everything is in good shape.
With the spark plug out and when rotating the fly wheel there absolutley no compression so I guess the piston etc is gone.

What I'm thinking of is just buying a replacement engine and basically winding up with a 'new' lawn mower.

The model is a Sears 917 37630 (s/n 050796M 003707) with a Sears Roebuck (Tecumseh I think?) engine # 143966500

I think it's about a 6.5 HP

Any ideas/advice on locating a replacement motor and the approx cost...?

This is actually eleven years old (manufactured on May 7, 1996, per the chassis' serial number), are you sure you want to do anything with this? I wouldn't but if you still do then you will find it difficult to find a suitable replcacement engine other than an exact replacement from Tecumseh. And the engine, originally, was a Tecumseh Vector engine and, in my opinion, is the worst small engine ever produced for walk-behind lawn mowers. I say keep looking for a different lawn mower. Just my opinion.

You said there is no compression when the spark plug is out and you turn the flywheel ??
The spark plug has to be installed to check compression.
Am I missing something here ?
thanks,