Can be bolted into just about any Subaru (in the US, everything except the 360 and Justy with very little work). Will bolt to any EJ/EZ/FA/FB transmission (basically anything since 1990, EA82 hung around in the Loyale until 1994). Will bolt to an EA81/EA82 transmission with an adapter plate.
It's considerably longer than any other engine, so depending on the chassis, radiator will have to be moved at least a little.
The challenging part is the electronics. Do you have the ECU and wiring harness? I assume there was some sort of plan on running it in the plane. The bulkhead harness (behind the dash, running up into the engine bay) has to be removed and considerably modified to graft the ECU and it's wiring for the 3.3 into the receiving car.
Fairly common swap into the '90s models, as they're much lighter. A '90s Impreza with a 3.3 will walk away from a stock STi in a straight line.
Engine code is an EG33. Google "EG33 Swap" will yield a flood of information, and obviously you can refine it down from there.
Not much market for them. SVXs were notorious for transmission issues, and the engines are very stout, so there's lots of them out there. Service parts are becoming scarce, most can still be sourced, but in 5-10 years? Probably not.