If you do the swap I would spring for a Painless or similar coversion harness, unless you really enjoy poring over diagrams and soldering wires (which you might...I don't know...). Integrating a factory harness is a days-long chore and involves aspects that can be simplified/eliminated in an older vehicle, which you can avoid by letting those suppliers do the work for you.
If you're keeping the engine stock, the factory computer/prom will work fine, there will be no VATS issues from an '80s system and the MAF (as opposed to speed-density) scheme will handle minor changes. All the modules etc. that look like such a mess in the Vette get a little easier to figure out when you've got them laid out on the living-room floor.
That said...first-year '85 TPIs are not the most desirable, '86-89 are a more sophisticated and reliable deal. TPI units in general appear to be losing favor, and GM seems to be discontinuing some support. Sweet as that motor looks, I might do more investigation before investing a lot into it.
My own TPI swap into a newer El Camino, integrating harnesses/retaining effective ESC and staying CA smog-legal, has been an on-again/off-again project for years and has yet to be completed thus I cannot say I'm the expert here.