Jeff - if you go down the replacement engine route - remember DO NOT TRASH
your old engine until you have the replacement fitted to your snow blower.
I make this comment because whilst sourcing a direct replacement engine (one that has identical base foot print, shaft height, length & diameter) should be easy enough (in fact you may not even have to replace your Tecumseh with another Tecumseh - coz in the size range there are often B&S or Honda options that will fit just fine).
This issue with retaining your old engine is that you will almost certainly need some of the linkages / control connection parts from your old engine.
The biggest problem with engine transplants is getting throttle / choke connections to mate up, as the OEMs often spec their own linkages - and chasing all over the place looking for these little bits & pieces is a total PiA
- so keep all those bits off your old engine and the transplant should be relatively painless (except for the $$$s