the 300zx belt is pretty long, but the longest? The ZR1 and Northstar are chains IIRC, the Lotus V8 has a pretty long one. The VW "W" engines I think are all chains. 3000GT is pretty long too. NSX is long, but deosnt wrap around too many idlers or other pulleys, so that probably not it.
this site ONE of the longest - and I saw this too, so that is why I posted the thread. One of my friends who recently got a job working on Porsches say that this is it, and I questioned him as to the possibility of it being something else, and he wasn't budging. So until someone finds one longer . .