The short story is we have a 91 Tracker with an 8v that could use a new engine.  We have a 92 Tracker 16v minus computer and wiring.  How much has to be done to swap to the 16v?

Do we have to swap the entire wiring harness and the computer, or can you just run the extra wires for the multi-port fuel injection over and swap the computer, leaving the rest of the wiring in tact?
The computer plugs are different....so the best/easiest way to do it would be just to swap the entire wiring harness and ECM (which I guess it looks like you don't have).
Can you just swap the lower end, keeping the 8v head and use the good block from the 16v?  Most places I have found have said this is a possibility, but it might turn your Zuki into an interference engine.
You can swap just the block.  The pistons have different valve cutouts in them, between the 8V and 16V.....so it may turn it into an interference engine......you could swap the pistons too, if they measure out the same.....then you wouldn't have to worry about it being an interference engine.
Would it be easier to just strip the Tracker and find someone willing to swap parts+engine for a good 8v?