[racer]

The other issue working against future value is time. As the cars get older, folks will buy up the "original" ones first. I see a huge demand for long hoods with original motors and condition, and less demand for those with large motors/flares/mods.

Given that your car has 200K miles already(?) I would simply do the 3.6 upgrade. Not sure what 3.6 motor prices are and depending on the year how much of the "other stuff" -ie, coolers, suspension to deal with heavier motor etc you would want to do or could afford to do.

I recall a friend doing a 3.6 conversion into his '77 and it was a LOT of money imho. It might be cheaper overall to rebuild your current known motor, maybe add a more open exhaust and chip and keep it as is. I imagine some 3.2 savvy engines are getting 15-20hp over stock ratings (which would get you close to a stock 964 3.6 motor)