Think about this for a second - why buy a "running donor" with the V6 just to transfer it to your Tracker? Why not buy it and run it and get rid of the Tracker? Yes - I understand your Tracker is a two door convertible and the donor will be a four door hard top.
Yes, you can swap the V6 into the Tracker - BUT - you're going to need to swap the transmission along with it, as well as the ECU and wiring harness, you're going to need custom exhaust, and possibly the drive shafts as well, depending on the tires you're running, you might want to keep the original axles or you might need to swap those as well, so really the only way to achieve this swap would be to buy a complete, running donor. I just don't see it as economical unless you're lucky enough to get a cheap donor with a good drive train, and you have the space, facilities and tools & experience to do the work yourself.
You might be able to broaden your J20 search a little - the J20a was also used on the Aerio